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 Post subject: How Scopes Work

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Here Is How Scopes Work

A telescopic sight can have several adjustment controls.

• Focusing control at the ocular end of the sight – meant to obtain a sharp picture of the object and reticle.
• Elevation or vertical adjustment control of the reticle.
• Zero-stop elevation controls can be set to prevent inadvertently dialing the adjustment knob "below" the primary zero (usually 100 meters or 100 yards for long-range scopes), or at least prevent dialing more than a couple adjustment clicks below zero. This feature is also useful on long-range scopes because it allows the shooter to physically verify the elevation knob is dialed all the way down avoiding confusion regarding the elevation status on two- or multi-revolution elevation knobs.
• Windage or horizontal adjustment control of the reticle.
• Magnification control – meant to change the magnification by turning a ring that is generally marked with several magnification power levels.
• Illumination adjustment control of the reticule – meant to regulate the brightness level of the lit parts of the reticles crosshairs.
• Parallax compensation control.


Image


Most contemporary telescopic sights offer the first three adjustment controls. The other three are found on telescopic sights that offer a variable magnification, an illuminated reticle and/or parallax compensation.

The front lens system (called objective lens) focuses the image of the target on the crosshairs that are permanently positioned inside the scope. Images (targets) at various distances need have the front objective lens adjusted so that the target is in focus. Scopes that do NOT have an adjustable objective are typically focused at 150 yds (for hunting) or 50 yds if they are a "22" scope.
Those scopes that are less than 10 power, usually have a compromise focus and work well enough for the intended usage.

The adjustable rear lens system (called the ocular) is to focus the rear lens system for your eye. When adjusted correctly the scope crosshairs should appear sharp and contrasty. The adjustment typically will not accommodate eyes that need lots of correction. The only way to tell is to take off the glasses and attempt to get the cross hairs sharp and contrasty. But do not look at anything other than the clear sky whenever adjusting the rear focus adjustment. In fact do it first before ever using the scope. Once set for your eyes it never needs to be adjusted again.

After adjusting the rear elements (ocular) you can then adjust the front objective lens system for image sharpness if the scope has an adjustable objective. Do NOT use the rear element to adjust the image of the target for sharpness. If you do that you may introduce parallax error and if you do not have your eye dead center in the scope optics then your bullet will not go where the crosshairs indicate.

A final test is to get the gun mounted firmly (motionless on a bench) pointed at the target. Look through the scope without moving the gun to see if the crosshairs move on the target when you move your eye a bit off center of the scope. If the crosshairs move on the target then you have parallax error and need to go through the adjustment procedure again for that target distance.
If you have the rear lens system adjusted correctly you only need to adjust the front lens system to eliminate the parallax error and focus the target.

You wear progressive lens glasses normally but you can not use them when shooting with scopes. You have to revert to a pair of glasses that has only single correction for distance or a pair of regular bifocals using the distant part of the lens. You can not find a scope that has enough correction for my eyes such that you could use the scope without glasses.

Hope this helps.

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Last edited by Mian Jee on Sun Nov 18, 2012 12:09 pm, edited 1 time in total.

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 Post subject: Re: How Scopes Work

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Excellent tips Mian Jee sb you are a expert of scopes.


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 Post subject: Re: How Scopes Work

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Carl zeiss wrote:
Excellent tips Mian Jee sb you are a expert of scopes.


hahaha....No Sir Jee...I'm no expert in any thing,
(btw, you are the first person in my life who called me an expert) :mrgreen:

I just collected it from many sources, Sort the basics, Compiled it & post it here for all.

That's it !...

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 Post subject: Re: How Scopes Work

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Nice share Mianjee. I think it's more relevant in the basics section and moving it there.

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 Post subject: Re: How Scopes Work

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MJ bro,
Expert or not, you sure are 'ustad jee'.
Thanks for the informative share.

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 Post subject: Re: How Scopes Work

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very informative compilation, mian G I am ur fan.

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 Post subject: Re: How Scopes Work

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Mustanir wrote:
very informative compilation, mian G I am ur fan.


Thank you so much Mustanir Bhai,

But right now, I need a blanket rather than a fan... :lol:

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 Post subject: Re: How Scopes Work

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Mian Jee aap ko blanket hee nahi chaiyaa thaa.. Heater lay laytay... jaisai marzi ayee... FAN aur BLANKET dono ka maza EK SAATH.. BRAUN ka heater.. Wah... Mian jee GARAM ho gayee ...

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 Post subject: Re: How Scopes Work

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This is an extensive post that I wanted to make since some time.. but was too busy.. to cajole my strength...

the website is http://www.about-shooting.com/Riflescop ... rmance.php

How to choose the best riflescope? Scope manufacturers strive to offer a scope for almost every conceivable shooting and hunting activity. Scopes are available with a variety of magnifications, reticles, click adjustments, objective lens diameters, scope tube diameters, finishes, features, accessories, and . . . the list goes on. There are so many options available for riflescopes. As you may have discovered, there are hundreds of scope models available from dozens of manufacturers. But no particular scope is ideal for every shooting activity and situation. It is up to you to order the best scope for your situation. But how will you ever sort through so many options?

To make your choice easier, scope selection can be separated into two areas: optical performance and features. This article provides information about scope optical performance.

OPTICAL PERFORMANCE
Scopes have become popular because they have advantages over sights. Aiming is easier with a scope than with open sights. Targets tend to hide behind the front sight. There is not a front sight to hide the target when aiming with a scope. The target is visible around the reticle aiming point because the scope reticle appears to be imposed directly on the target. A shooter can aim carefully without eyestrain while sighting with a scope because he or she does not have to rapidly switch focus between the scope's reticle and the target while aiming with a scope.

Also, a quality scope allows the shooter see better in low light conditions than sights. A scope will direct the ambient light rays that form the target image into the pupil of the shooter's eye where the rays can do some good. That is more than sights will do. In fact, a front sight, being directly between the target and the shooter's aiming eye, will block much of the light from the target. This could make the target seem to disappear in low light conditions. But the most obvious advantage is magnification.

MAGNIFICATION


Magnification is usually the first specification a shooter considers when shopping for a scope and it is one of the first criteria listed on scope specifications. With riflescopes, as with other optical devices, magnification power is simply expressed as "power". Power is indicated with the scope specifications by the letter "X". The digit or digits before the "X" indicate the scope's power. (The digits after the "X" indicate the scope's objective lens diameter in millimeters). Some scopes have fixed power. Their power cannot be changed by the shooter. On the other hand, variable power scopes allow the shooter to adjust the scope's magnification within its power range to match the current situation. Variable power is expressed with a hyphen to indicate the power range (from lowest to highest) followed by the letter "X". (For example: 3-9X)

This is a small grid that could show the preferable choices for scope magnification according the game and the power that may be chosen.

Hunting Activity Environment Fixed Variable
Dangerous Game Thicket / Jungle <2X 1-4X
Deer / Bear Woodlands 4X 2-6X
Deer / Sheep Mountains 6X 3-9X
Deer / Bison Plains 8X 4-12X
Varmint / Predator Farmlands 14X 6-18X
Varmint / Predator Plains 18X 8-24X


Not only does magnification make the target seem closer but, combined with precise windage and elevation adjustments, increases shooter confidence. With adequate magnification a shooter does not merely aim at the target. No; A shooter can choose where to aim on the target and, with a precisely zeroed scope, can hit where aiming.

Well, with all that going for scopes, why not just order the scope with the highest magnification, the finest reticle, and the largest objective lens? Magnification is an important consideration when choosing a scope. That does not mean the highest power available is the best option. Other optical parameters such as field of view, light transmission, and eye relief decrease as magnification increases. These criteria may be even more important than magnification in some situations. Too much magnification can actually be detrimental in certain situations.

FIELD OF VIEW

Consider field of view. Field of view (FOV) is the width of the area that is observable through the scope. FOV for riflescopes is commonly expressed in feet of width at 100 yards distance (or meters of width at 100 meters). Because FOV is an angular measurement, it widens in direct proportion to the viewing range. The FOV at 100 yards actually means FOV per 100 yards of viewing distance.

All scopes have a limited field of view. Limited field of view is a major disadvantage inherent with optical devices. A shooter cannot see anything outside the FOV. A narrow FOV makes finding a visually spotted target with a scope difficult or tracking a moving target nearly impossible. A wide FOV is desirable. Wide FOV helps a hunter sight game with the scope before the game gets away - or before the game gets the hunter.

What does field of view have to do with magnification? Magnification adversely affects FOV. The higher magnification, the narrower FOV. The lower the power, the wider the FOV. A scope cannot have both high magnification and wide FOV. The FOV of variable power scopes can be widen only so much by decreasing power. High magnification or wide FOV? You must decide which is more important for the intended shooting activity and conditions before ordering a scope.


EXIT PUPIL

Magnification also affects the size of a scope's exit pupil. Exit pupil diameter is not a physical dimension. Rather, it is an optical dimension formed by the light beam emitted from the scope toward the shooter's eye. The larger the exit pupil, the wider the beam of light directed to the shooter's eye.

Exit pupil is often listed with other scope specifications. A scope for hunting in low light conditions should have about a 5mm exit pupil. (A 5mm scope exit pupil closely matches the 5mm dilation of a normal human eye pupil in low light.) A scope with an exit pupil less than 5mm will not be a good choice for hunting in the early morning or late evening. Such a scope will work just fine during the day when the shooter's eye pupils have constricted to as small as 2mm due to bright light anyway.

Exit pupil is influenced by a scope's magnification and its objective lens diameter. The objective lens is the closest lens to the target; the first lens of a series of lenses.

The objective lens - the farthest lens from the shooter - affects the diameter of beam of light exiting the scope toward the shooter's eye. Exit pupil (in millimeters) is calculated by the dividing a scope's objective lens diameter by its magnification. (Scope objective lens diameter is usually listed immediate after its power and expressed in millimeters.)

Objective lens diameter (in mm) divided by power = exit pupil (in mm)

Examples:
30mm ÷ 3 power = 10mm
30mm ÷ 6 power = 5mm
40mm ÷ 20 power = 2mm
50mm ÷ 10 power = 5mm

We can conclude from the equation that, for any objective lens diameter:

the lower the magnification, the wider the exit pupil; and
the higher the magnification, the narrower the exit pupil will be.

And, for any magnification:

the wider the objective lens diameter, the wider the exit pupil; and
the narrower the objective lens diameter, the narrower the exit pupil will be.

Therefore, a large objective lens is necessary on a high power scope just to have a sufficient exit pupil for aiming in low light conditions.

Essentially, the size of the objective lens determines how much light enters and magnification determines the size of the light column that exits the ocular lens toward the shooter's eye. Exit pupil merely describes the size of the light disk that reaches the shooter's eye. Exit pupil does not influence the brightness of the light beam emitted from the scope. The brightness of the light disk transmitted through the scope is influenced by lens quality - particularly lens coatings.

LENS COATING

In addition to exit pupil size, lens quality also affects how well a scope delivers light to the shooter's eye.

A lens would ideally transmit all the light that reaches it surface. However, no lens is perfect. Reflection, refraction, aberrations, absorption, and glare reduce the light transmittance of every lens to some degree. Each lens within a scope has both front side and reverse side reflection. Light that is reflected is light not transmitted to the shooter's eye. Even simple scopes contain several lenses. Each of those lenses reduce light transmission a bit. Reflection through a low-quality, multi-lens scope could reduce light transmittance as much as 50%. Most modern scopes have some form of anti-reflective lens coating to reduce reflection, thus, increase light transmittance to the shooter's eye. Good scopes have fully coated lenses or even multi-coated lenses. Quality scopes have fully multi-coated lenses. Scopes with fully multi-coated lenses allow 95% of the light to be transmitted to the shooter's eye. Order a scope with fully multi-coated lenses if you anticipate hunting early morning or late evening.

sufficient exit pupil + coated lenses = good light transmittance

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 Post subject: Re: How Scopes Work

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OBJECTIVE LENS DIAMETER

As described above, exit pupil size is a major factor that affects scope light transmission and that exit pupil is determined by objective lens diameter and magnification. A larger objective lens makes a larger exit pupil for any power level. A large objective lens is necessary on a high power scope just to have a sufficient exit pupil to shoot in low light. You could order a scope with a large objective lens from the start if you plan to hunt in low light. Forty millimeters or larger.

So why not order a scope with the largest objective lens available? One that has a large objective lens out of proportion to its power. Because a scope with a large objective lens must often be mounted too high for the shooter to get a solid stockweld.

A large objective lens must be enclosed within a large objective lens bell. Since there must be space between the objective lens bell and the top of the barrel, a scope with a large objective lens must be mounted high to clear the barrel. With a scope mounted too high, the shooter must raise his cheek off the buttstock comb to align his eye with the exit pupil. If the shooter's eye is not in the same position relative to the scope it was when the scope was zeroed, parallax error will occur. Also, since the shooter's head may not recoil with the rifle without a solid stockweld, eye relief becomes an issue.

An extremely large objective lens larger is appropriate only if you will be using high magnification to shoot in low light conditions. If you plan to shoot in low light conditions with high magnification, by all means, order a scope with an extremely large objective lens. But do not order a scope with an extremely large objective lens just for the sake of having a scope with an extremely large objective lens.

EYE RELIEF

Eye relief is the distance the viewer's eye must be from the ocular lens to allow the viewer to see the whole exit pupil. The viewer will see a dark area around the perimeter of the field of view if the viewer's eye is closer than the minimum eye relief distance or farther than the maximum. A reasonably long eye relief is desirable in riflescopes; longer than with most other optical devices. Eye relief must be sufficient to allow the rifle to recoil against the shooter's shoulder without allowing the rim of the eyepiece to gash the shooter's eyebrow. The heavier the recoil, the longer the eye relief must be. Even light recoiling rifles should have scopes with at least three inches of eye relief. Medium recoil rifles at least 3+1/2 inches of eye relief. And heavy recoil rifles, at least four inches.

The problem is that eye relief decreases as magnification increases. Increase the power of a variable power scope and you'll decrease eye relief. Magnification must be low enough to allow sufficient eye relief on heavy recoil rifles. Lightweight, high-power rifles and high magnification scopes, with their short eye relief, are not compatible.

Scope manufacturers can actually make scopes with much longer eye relief. (Some make handgun scopes with extended eye relief.) So why don't they make riflescopes with longer eye relief? Magnification is one reason as previously stated. Another reason is field of view (FOV). Increased eye relief results in reduced FOV. FOV suffers if eye relief is extended beyond what is needed based on intensity of recoil.

Do not order a scope with a 3/4-inch main tube for a centerfire rifle even if you can find bases and rings to mount it. Scopes with 3/4-inch scope tubes are designed specifically for air rifles and rimfire rifles with very light recoil. Such scopes are designed with a short eye relief - so short that eyepiece could strike the shooter's eye during recoil if they were mounted on a centerfire rifle.

High magnification or long eye relief or wide FOV? You cannot get all three in the same scope.

MIRAGE

A scope will magnify anything within its field of view including something you do not want to be magnified - mirage. Mirage is image blurring and distortion caused by rising heat waves. Mirage will cause the target appear to distort with the breeze. Mirage is present to some extent wherever the surface is warmer than the air above it. Mirage is most noticeable when the line of sight is parallel to and close to the surface. Also, depth of mirage increases as range to the target increases. The target must be viewed through the mirage. Because mirage is between the scope and the target, magnification will magnify the mirage to a greater extent than it magnifies the target. The higher the scopes power, the more intense the mirage will seem. The view through a low power scope will be less distorted by mirage than the view through a high power scope.

You should reconsider ordering a high power scope if you anticipate frequently shooting over a hot, flat surface.

TREMOR

Tremor is something else you do not want magnified. Whenever a shooter grasps a firearm to shoot, a certain mount of unintentional movement is imparted on the firearm by the shooter. Even a shooting rest may not eliminate all tremor. Tremor is noticed in two ways - the inability to discern target details and the drifting of the reticle about the intended aiming point. Scope magnification exaggerates tremoring. A drifting reticle could frustrate the shooter so much that the shooter may just yank the trigger when the reticle finally does drift across the aiming point just to get the shot off. Rifles with high-magnification scopes should be supported by a rest to shoot.

Do not order a high power scope if your shooting will be done offhand or from uneven terrain.

CONCLUSION

You know what shooting activity you intend to participate in before you order a scope. You know the environment you will be in and the method you will use. And you know what rifle and cartridge you will use. Now you just have to order a scope that matches. Order a scope with enough power but not too much. The scope you order should have only slightly more magnification than the cartridge effective range requires. Anymore magnification could be a liability.

Remember, a scope is an aiming aid; not a scanning or spotting aid. Order enough scope power to aim with but use a binocular or a spotting scope to scan for targets. Besides, if you use a scope for scanning you will also be aiming - aiming at something you do not intend to shoot.

Only you can decide which scope to order. Uninformed shoppers order scopes with too much magnification. Consider yourself informed.

FEATURES

Obviously a riflescope's optical performance will help you to see targets better. But you are looking for a riflescope to help you aim as well. Scopes have features to help you to sight in and aim at targets also. Features such as reticles, internal windage click adjustments, and elevation click adjustments. Without such features a riflescope would merely be a telescope that can be attached to a rifle. Optional features such as parallax adjustments, variable-power, optical rangefinders, and bullet drop compensators are available with some models to further increase scope utility.

No single scope is ideal for every shooting activity. A particular scope may fit one shooting activity well, be a compromise for some activities, and be unsuitable for others. In addition to optical performance (as explained in a related article), you must decide which scope features best serve your shooting activity. With so many features available, how do you choose the best scope? This article describes some important options you should consider before ordering a scope.

FIXED OR VARIABLE POWER

Riflescopes have either fixed-power or variable-power. The magnification of a fixed-power scope is set in the factory and cannot be changed by the shooter. Its power is listed with its specifications and is indicated with the letter "X" (for example: 10X).
The magnification of a variable-power scope is adjusted with its power ring.

The magnification of a variable-power scope, on the other hand, is adjustable within its power range by the shooter. The power range of a variable-power scope is shown with a hyphen between minimum and maximum power and is also indicated by the letter "X" (for example: 3-9X).

Variable-power allows shooters to adjust magnification as well as the other parameters magnification affects - field of view (FOV), exit pupil diameter, and eye relief. The shooter can adjust the magnification of a variable-power scope to match the shooting activity and the current conditions.

The lowest power setting provides the widest field of view for making quick, unexpected shots at close range and for tracking running game. A hunter can carry a rifle with the scope power set at low power to take quick shots at close range then crank up the power to take slow, deliberate shots at longer ranges. The wider FOV of low power settings helps to locate a target in the scope previously seen visually before zooming in to take a precise shot. Finally, the hunter could decrease power again if the distortion caused by mirage becomes a problem.

Due to their versatility, variable-power scopes far outsell fixed-power scopes. So why even make fixed-power scopes? Because some shooters still prefer fixed-power scopes. These shooters prefer fixed-power scopes because they are generally lighter, shorter, more durable, more reliable, and less expensive than variable-power scopes of similar quality. fixed-power scopes have fewer parts because they do not have a power adjustment system. There are fewer parts to make and install during manufacturing and fewer parts to break or wear out during use. Many competition shooters prefer fixed-power scopes because not being able to adjust magnification, FOV, and exit pupil is more acceptable to them than even the slightest change in zero that may accompany power changes. Besides, many owners of variable-power scopes set the power at one power level then rarely change it anyway. A fixed-power scope does not have a power ring

The power adjustment mechanism adds weight, complexity, and cost, therefore, variable-power scopes are generally longer, heavier, and more expensive than fixed-power scopes. The extra length is required to install the power adjustment tube inside the main scope tube. The power ring of a variable power scope is an external control linked to an internal mechanism. Not only does the power change mechanism increase complexity, but a variable-power scope must have a power ring groove cut through its main tube. The power ring groove is the weakest area of a variable-power scope tube. Also, the power ring is an area where moisture can seep in. The main tube of a fixed-power scope does not have a power ring groove or any of the potential problems of a power ring groove.

But do not be down on modern variable-power scopes. No. Quality, variable-power scopes are very reliable despite all their potential problems. The zero shift as power is changed on quality variable scopes is almost indiscernible. Modern scopes rarely leak around the power change mechanism (or anywhere else) anyway. The certain versatility of a variable-power scope overshadows its potential problems. Fixed-power or variable-power? You decide.

RETICLES

The primary purpose of a riflescope is to assist the shooter with aiming the rifle. Magnification will make the target appear larger, but aiming is the primary purpose of a riflescope. With that in mind, the scope manufacturers continue to improve and enhance reticles. The reticle of a riflescope is aiming reference within a scope. It is the presence of a reticle that distinguishes a telescopic sight from a telescope.

Reticles have evolved from simple crosshairs. Thick crosshairs were easy for the shooter's eye to find for quick shots at close range. But thick crosshairs could also obscure small targets at long range. On the other hand, fine crosshairs were useful for taking deliberate shots at stationary targets but blend with shadows and other dark backgrounds or disappear in low light making aiming difficult.

Dual thickness crosshairs combine thick crosshairs and thin crosshairs in one reticle. The thick sections that comprise the outer 9/10th or so of the crosshairs are available to make quick shots at close range or into low light. The middle 1/10th is thin for taking slow, precise shots. Although the dual thickness crosshair reticle was introduced in 1962, it is still popular because of its uncluttered efficiency and intuitiveness. Dual thickness crosshairs are known by several trade names depending on the brand of scope including "Duplex", "Truplex", "Dual-X", "Multiplex", and "Multi-X".

Center circle and center diamond reticles are basically dual thickness crosshair reticles with a circle or an open diamond around the thin sections of the crosshairs. The circle or diamond draws the shooter's eye to the center of the FOV for quick shots and retains thin sections of crosshairs for precise shooting.

The center dot reticle, also called an MOA dot reticle, is sort of like the opposite of the dual thickness crosshair reticle. It consists of a center dot that appears to be suspended at the intersection of thin crosshairs. The size of the center dot varies between scope models. Center dots subtend as small as 1/8 minute-of-angle (MOA) and up to one MOA depending on the model. (One MOA is about one inch per 100 yards of range.) Some shooters like the one MOA dot because this reticle facilitates quick shots at close range and believe that 1/8-MOA and even the 1/4-MOA dots are too small. Others like the 1/8-MOA dot for long range shooting. They believe even a 1/4-MOA dot obscures small targets. One dot size does not please everyone. Before you order a center dot reticle, have an idea of what kind of shooting you will be doing; then order the best size of dot accordingly.

Tactical reticles have become popular because they are not just aiming reticles. In addition to aiming, shooters can use mil reticles to estimate target range, adjust hold-over or hold-under, apply wind correction, lead moving targets, and correct for inclination or declination. Tactical reticles feature reference marks imposed on the vertical and horizontal crosshairs based on the milliradian (mil) measurement system. (A milliradian is angular divergence measured with any unit of length measurement at a distance of 1000 times that unit. For example, 1 inch of width measured at 1000 inches of distance is a milliradian as is one foot of width measured at 1000 feet, 1 yard at 1000 yards, and so on.) Although frequently called mil-dot reticles, tactical reticles may display mils as circles or lines as well as dots depending on the scope model. Tactical reticles are popular with varmint hunters and target shooters as well as law enforcement and military snipers.

Black reticles are indiscernible in low light against dark targets. Illuminated reticles solve this problem. Scopes with illuminated reticles use battery power to make the reticle glow either red or green. The reticle may be a dot, circle, or tactical reticle. These scopes do not amplify light as night-vision scopes do; they only illuminate the reticle to make it stand out from dark backgrounds.

INTEGRAL RANGE FINDERS

Optical rangefinders integrated within scopes require the shooter to estimate the size of the target then bracket the target between the two horizontal lines. The estimated range is read within the scope field of view adjacent to the appropriate horizontal line or one the power ring. If the target is a game animal, optical rangefinders are only reliable if the animal is standard-sized, exposes itself clearly, and stands broadside long enough to be bracketed. The estimated range will be wrong if the animal is not standard-sized or does not cooperate with the hunter.

Unlike optical rangefinders, laser rangefinders (LRFs) do not require the animal to be a standard size or to be entirely cooperative. Plus, laser rangefinders are far more accurate than scope-based optical rangefinders. However, handheld laser rangefinders are difficult to hold steady while taking readings. Wouldn't it be convenient if you could steady a laser rangefinder like you do while aiming a rifle? Wouldn't it be even better if you did not have to set the laser rangefinder aside then scramble to find the target in the scope also. Well, laser rangefinding riflescopes incorporate a laser rangefinder within a riflescope. Now, a shooter can aim at a target and range it simultaneously with a laser riflescope while steadying the rifle on a rest.

TRAJECTORY COMPENSATOR

Using a rangefinder, hunters can measure whether or not a game animal is within point blank range or even effective range. Some hunters may want to place their shot precisely although the game is within point blank range. In either case, a hunter must compensate for bullet trajectory to place the shot for a clean kill.

The hold-over / hold-under method and the click-up / click-down method are two methods used to compensate for trajectory when the target is at a range other than the zero range.

The hold-over method requires the shooter to aim above the vital zone the distance the bullet will drop at that range. Ballistic reticles are available with some scopes as an aid to using the hold-over method. Ballistic reticles have additional reference points, circles, or lines along the lower half of the vertical crosshair. The shooter aims using whichever reference point, circle, or line closest represents the trajectory at that range. The farther the target, the lower the reference line the shooter must use. The scope instruction manual indicates the subtension each line represents relative to the horizontal crosshair. The reference lines rarely match trajectory perfectly, but using a reference line is better than merely visualizing hold-over. The tactical mil reticle is one example of a ballistic reticle. BTW: there are Interchangeable trajectory compensation scales that slip onto the elevation turret

The click-up method of trajectory compensation is more precise than the hold-over method but takes longer to set up. Trajectory compensation is achieved when using the click-up method by adjusting the elevation dial the number of clicks appropriate for the range to compensate for bullet drop. Using the click-up method, you can aim spot on after the elevation dial is set correctly.

Some optical rangefinding scopes include a set of interchangeable trajectory compensating scales that slip onto the elevation adjustment turret. The scales place the click adjustments from a trajectory table directly on the elevation turret. The ring with the scale that represents the trajectory best is installed onto the elevation turret after the rifle is zeroed. While hunting, the hunter refers to the scale installed on the elevation turret to dial in the trajectory correction. Then the hunter can aim directly at the game. The hunter has actually rezeroed the rifle to the current shooting distance.

Some laser rangefinding scopes rely on the click-up method for trajectory compensation. Other laser riflescopes provide ballistic reticles. However, the latest laser scopes have internal ballistic computers. The shooter must program the scope with the trajectory. After programmed, the computer automatically repositions the electronic reticle to compensate for trajectory based on the range measured by the LRF. The ballistic computer also factors declination and inclination angles into the trajectory compensation.

CLICK ADJUSTMENTS

Elevation and windage on modern scopes are adjusted internally. Internal adjustments help a shooter precisely zero a scope to the rifle it is mounted on. In addition, elevation adjustments also provide a way for shooters who use the click-up method to compensate for trajectory.
Target knobs can be turned with the shooter's fingers.
Target knobs can be turned with the shooter's fingers.Target knobs can be turned with the shooter's fingers
Target knobs can be turned with the shooter's fingers

The click adjustments may be provided by target knobs that protrude from the scope main tube or by dials that are nearly flush with the tube depending on the model of scope. Dials are protected by removable caps to prevent damage. Dials require a coin or screwdriver to make adjustments. Target knobs can be turned with fingers. Knobs may or may not be protected by caps. Knobs on certain scope models have a locking ring that tightens to prevent the knob from being turned inadvertently.

Most shooters who use the click-up method of trajectory compensation prefer adjustment knobs. The click reference lines on knobs can be seen by the shooter while in a shooting position and adjustments can be made with minimum disturbance from the shooting position. However, knobs are more likely than dials to be damaged by boulders or snagged in brush while hunting. Therefore, target knobs are generally preferred by competition shooters and varmint hunters while dials are generally preferred by big game hunters.

You will want to be sure whether or not you have adjusted the correct number of clicks. Adjustment clicks must be discernible tactilely, audibly, and visually. Target knobs provide visual confirmation that the correct number of clicks actually were made. However, the reference lines on knobs will not be visible in low light. Therefore, clicks must be discernible by feel including with cold fingers or through thick gloves. Most scopes have 1/4-inch click values per 100 yards of range.

The click value indicates how far the bullet point-of-impact should move at the prescribed range. The actual distance each click value moves bullet point-of-impact is directly proportional to the range of the target. The farther the target, the more each click will move the point-of-impact on the target. The most common click adjustment value is 1/4-inch at 100 yards distance. (That is actually 1/4-inch per 100 yards of range.) Other click values are 1/2-inch and 1/8-inch at 100 yards (per 100 yards, actually). Occasionally clicks increments are expressed in minutes-of-angle (MOA) or some fraction of MOA. One MOA is 1.047 inches at 100 yards - very close to 1 inch at 100 yards. So for practical purposes, 1/4-MOA clicks can be considered 1/4-inch clicks.

Scopes with 1/8-inch click adjustments can be zeroed more precisely than scopes with 1/4-inch clicks. However, such fine clicks many be inconvenient for shooters who use the click-up method of trajectory compensation. Twice as many 1/8-inch clicks are required as 1/4-inch clicks to compensate for trajectory at any range. The full range of 1/8-inch clicks may not be sufficient to compensate for trajectory at extremely long-ranges - just where trajectory compensation is most needed.

TUBE DIAMETER

Riflescope main tubes are usually either 1-inch or 30mm diameter. Riflescopes with 3/4-inch diameter tubes are designed for air rifles or rimfire rifles. Scopes with other tube diameters, such as 27mm, 34mm, and 35mm, are rare. Thirty millimeter main tubes (about 1+3/16-inch) are slightly larger than 1-inch tubes. Thirty millimeter tubes of the same wall thickness have space for a few more internal windage and elevation click adjustments than 1-inch tubes. The 30mm tubes are also slightly more rigid than 1-inch tubes of the same wall thickness
OBJECTIVE LENS DIAMETER
The larger the objective lens diameter, the larger the exit pupil at any magnification. Hunters who intend to hunt in low light conditions should order a scope that has an exit pupil no smaller than 5mm. Exit pupil is normally listed with the scope specifications. If the exit pupil is not listed, divide the objective lens diameter in millimeters by scope power. Use the lowest power setting in this equation if the scope has variable-power.

A large objective lens is necessary on high magnification scopes just to have a sufficient exit pupil to shoot in low light conditions. So why not just order a scope with an extremely large objective lens even if you do not plan to shoot in low light? Because a scope with a large objective lens must be mounted high to clear the top of the barrel. There must be at least a 1/8-inch space between the objective lens bell and the barrel. With a scope mounted too high, your cheek may not be supported by the buttstock comb while aiming, causing inconsistent eye position. Parallax error will occur if the your eye is not in the same position that it was relative to the scope when the scope was zeroed. Do not order a scope with a large objective lens just to have a scope with a large objective lens. You should order a scope with an extremely large objective lens - larger than 40mm - only if you plan to shoot in low light with a high magnification scope.

PARALLAX ADJUSTMENT
Parallax is the perceived relative movement between two separate stationary objects at different distances as viewed by an observer from various locations. Scope parallax refers to the perceived drifting of either the target image or the reticle whenever the shooter's eye position changes vertically or laterally while aiming with a scope. If the target is stationary and the scope is steady, perceived movement of the reticle or target may be due to shooter eye movement. Parallax can cause shot placement error.

Parallax error is present whenever the target image and reticle are not on the same focal plane and the shooter's eye is not consistently realigned with the scope's exit pupil before each shot. Ideally, the target image would be located on the reticle. The reticle and target image will appear to be conjoined in this case. There will be no reticle drifting no matter where the shooter positions his eye within the boundary of the exit pupil.

The location of the target's image within the length of the scope depends on the real target's distance from the scope's objective lens. Just as the range to the target varies between different shooting situations, so will the target image within the scope. As a result, the current target's range rarely causes the image focal plane to coincide with the reticle position within the length of the scope. Moving closer to or farther from target to get the focal plane to coincide with the reticle is rarely practical. So shooters must either optically adjust the focal plane to coincide with the reticle or simply accept the possibility of parallax error.

Adjusting the focal plane to the reticle requires the scope to have a parallax adjustment mechanism. Not all scopes have a parallax adjustment mechanism. Many scopes have parallax set at the factory for some intermediate range depending on the expected use of the scope. Parallax on these scopes cannot be adjusted by the shooter. The factory set range is typically 50 yards for scopes intended for air rifles and .22 rimfire rifles and 100 yards for scopes intended for big game hunting. Some parallax error is acceptable in big game hunting scopes because within 200 yards the maximum parallax error does not exceed the vital area of big game animals.

However, competition riflemen, varmint hunters, and other shooters who regularly shoot beyond 200 yards generally prefer scopes with adjustable parallax. Parallax adjustment allows the shooter to position focal plane within the scope to coincide with the reticle's position. Parallax can be readjusted each time the range changes. Scopes with parallax adjustment have either an adjustable objective lens or a side knob parallax adjustment mechanism.

The objective lens bell is twisted to eliminate parallax with an adjustable objective (AO) lens system. Reference marks around the objective bell represent various ranges to help the shooter make a rough adjustment. If a rest is available, fine parallax adjustment is done by steadying the rifle and viewing through the scope at the target while twisting the objective bell. Parallax has been eliminated when the objective lens has been twisted to a position where no target to reticle drifting is noticed whenever the shooter makes slight head repositions.

Scopes with a side knob parallax adjustment system include a knob on the left side of the main tube adjacent the elevation adjustment. The knob also has reference marks to help make rough parallax adjustments. The rifle must also be steadied on a rest while viewing through the scope to make fine adjustments.

The adjustable objective lens system is easier to learn and is sturdier than the side knob adjustment system. However, because the adjustable objective lens is at the opposite end of scope from the shooter, the shooter cannot view the range reference marks on the surface of the objective bell while in the prone shooting position. On the other hand, the reference marks of the side knob can be viewed from any shooting position. Also, a side knob is easier to reach while viewing through the scope to make fine parallax adjustments than an AO, especially with long scopes.

FINISHES

Now let's consider scope outer surface finishes. Nearly all models of scopes are available with gloss (shiny) black or matte (flat) black anodized finishes. Some models are available with "silver" finishes. Maybe you want a scope finish that matches your rifle receiver - gloss black to match a black oxide rifle finish, matte black to match a parkerized finish, or silver to match stainless steel. Scopes with silver finishes are normally mounted only on competition rifles because camouflage is not an issue with competition rifles. Some models of scopes are available with camouflage finishes if you really are concerned about camouflage.

CONCLUSION
There are so many riflescope models with countless features currently on the market. Choosing the best riflescope for your shooting activity can be difficult. Perhaps this article has helped you sort through some of the options to decide which scope to order.

_________________
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 Post subject: Re: How Scopes Work

Sniper

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Assuming you have selected a riflescope to go with your rifle, you must securely attach it to your rifle. Scope bases and rings serve that purpose. The bases attach to the rifle receiver to provide a foundation for the rings. The scope bases are also a sort of adapter that allow almost any scope to be mounted on almost any rifle. The rings attach to the bases and hold the scope. The mounting system must secure the scope during transportation, handling, and, especially, during recoil.
Due to the popularity and availability of riflescopes, modern rifles are designed to accept a variety of scopes. The safety levers and bolt handles of modern bolt action rifles are positioned to be operated without interference from scopes. Modern rifles, including lever action rifles, typically eject cases to the right instead of directly upward where the cases would strike the scope. Twenty-two caliber rimfire rifles often have two parallel lengthwise grooves milled near the top of their receivers to attach scope rings directly to the receiver. Some rifles even have scope bases as an integral part of the receiver. And rifles that do not have integral scope bases are drilled and tapped for scope base screws at the factory. Such feature have made mounting a scope much easier.

Despite these design features, you still must select the correct combination of bases and rings that will accommodate the length of riflescope, scope tube diameter, objective lens bell diameter, and eye relief. In addition, the bases must also fit the make of rifle and its receiver length. Luckily, an assortment of base lengths, ring sizes and heights, finishes, and styles is readily available to mount almost any scope on almost any modern rifle. In fact, there may be several combinations of bases and rings that will work. You must decide which combination best meets your needs. This article may help you sort through the options available to select the correct scope bases for your rifle. So keep reading.

Your rifle may have integral scope bases or scope rails. Models offered by Ruger®, Sako®, and BRNO CZ® have integral bases. Tikka® rifles have integral scope rails. If so, you may choose to attach the ring mounts directly to the integral bases or mount additional bases on top of the integral bases. (You can skip to the next article in this series, Selecting Scope Rings, if you decide to attach rings directly to the integral bases.) If, in some rare case, you cannot find rings to fit integral bases, you may have to mount additional bases on top of the integral bases then select rings that will fit the new bases.

Unless your rifle's receiver has integral scope bases or rails or you will be mounting a scope on a .22 rimfire rifle with scope ring grooves, you must select the type of scope bases for your rifle.

ATTACHABLE SCOPE BASES


Attachable Scope Bases

Attachable scope bases get attached to the rifle receiver with screws. There are many varieties of attachable scope bases available. Since they are all designed to maintain scope security during rifle handling and recoil, the type of bases to install is usually a matter of preference. The two most common types of bases are the cross-slot rail type (also called the Weaver-style) and the rotating-dovetail type (often called the Redfield-style). Both Weaver-style (cross-slot rail) and Redfield-style (rotating-dovetail) bases and rings are currently available from several manufacturers. Quick-release bases are another type. There are a few other types, but the cross-slot rail, tactical, rotating-dovetail, and quick-release types are detailed in this article.

Cross-Slot Rail Scope Bases

Cross-slot (Weaver-style) scope bases are a type of attachable scope bases. After the bases have been attached to the receiver, the scope rings, which are sold separate from the bases, are attached to the bases. The front ring and rear rings both attach to the bases the same way. New rings for cross-slot rail bases of the equal height are interchangeable between front and rear bases. (New rings are interchangeable between front and rear bases but the bases themselves may not be interchangeable between front and rear positions on the receiver.) The bottom halves of the scope rings are placed on top of the cross-slot rail base then clamped to the sides of the base. Lateral screws are tightened to secure the clamps to the rail.
Tactical Scope Bases

Also called "Picatinny" bases, tactical bases are heftier than standard scope bases. They resemble cross-slot bases with many more, evenly-spaced cross-slots. Tactical bases, with their slightly wider (0.206" compared to 0.180") cross-slots, accept both tactical scope rings and standard weaver-style cross-slot rings. However, standard cross-slot bases will not accept the thicker recoil tab and larger cross-bolts of purely tactical rings.Tactical bases have slightly wider cross-slots than standard cross-slot bases.

In addition to police and military riflemen, extreme long-range varmint hunters and competition shooters often install tactical scope bases on their rifles. Besides being heftier than standard bases, the tactical bases with 10 or 20 MOA (minutes-of-angle) of forward cant provide some of the additional elevation required to shoot long range. The built-in forward cant eliminates the need to install a shim beneath the rear scope base to sight-in at targets beyond 600 yards.
Rotating-Dovetail Scope Bases

The front and rear rings each attach to their respective bases differently in the rotating-dovetail type base. A dovetail stud protrudes from the bottom of the lower half front ring. This stud fits into a recess in the front scope base. The stud locks the front ring into its final position when the ring is rotated 90 degrees. On the other hand, the bottom of the rear ring is flat. It has no protruding stud. Instead, two laterally opposing windage screws in the rear base secure the rear ring. The lateral screws allow coarse external windage adjustments.

A variation of the rotating-dovetail type is the dual rotating-dovetail. Dual dovetail bases and rings provide more security for scopes mounted on magnum rifles. The front ring of the dual dovetail system attaches to its base the way described above for the single rotating-dovetail front ring. However, the rear ring also attaches to the rear base the same way the front ring attaches to the front ring. There are no laterally opposing windage screws on the rear base. Hence, the rear ring of the dual rotating-dovetail system is not adjustable for windage. (All the windage adjustments, as well as elevation adjustments, must be made with the scope's internal adjustments.) The advantage of the dual rotating-dovetail system over the rotating-dovetail is its security. There are no laterally opposing windage screws to work loose as with the single rotating-dovetail system. (Like the new front and rear cross-slot rings, new rings for the dual rotating-dovetail system are also interchangeable between front and rear bases.)

Quick-release scope bases and rings

A quick-release mounting system is another option. Detaching the scope and storing it separately may prevent damage to the scope. Quick-release mounts allow the scope rings to be easily separated and reattached to the bases. The quick-release bases do not detach from the receiver; the rings, with the scope installed, detach from the bases. Quality quick-release mounts allow the scope to be reattached with very little change in zero. You may settle on a quick-release mounting system if you will be storing your rifle in a confined gun safe or will be transporting it commercially. Also, a second scope installed within its own rings and previously zeroed could be a spare scope if the first scope has been damaged on a hunting trip. Other reasons for choosing a quick-release mounting system include the ability to change scopes to match the hunting environment or to detach the scope to use the sights. Or, since you normally hunt with only one rifle at a time, a single scope with quick-release rings could be switched between rifles with compatible bases.

Some quick-release systems require both special bases and special rings. Rotating two thumb levers on the left side of the base forward engage a stud protruding beneath each ring. The rings are pulled down and secured solidly to the base. Rotating the thumb levers rearward releases the rings.

Other quick-release systems consist of quick-detach rings that attach to standard cross-slot bases. Instead of requiring a wrench or screwdriver, one thumb lever on each of the rings is used to tighten and loosen the ring clamps.
One-Piece or Two-Piece Scope Bases

A one-piece dovetail scope base spans the ejection port.

A two-piece scope base does not span the ejection port

Whether you decide to attach cross-slot rail, rotating-dovetail, or quick-release system, you must choose between a one-piece base design and a two-piece base. Two-piece bases can be purchased as a set of two (one front and one rear base). A one-piece base is one long base that spans from the front of the receiver over the ejection port to the rear ring of the receiver. Cross-slot rail, rotating-dovetail, and quick-release bases are available in both designs.

Some shooters claim the two-piece design makes it easier to load a bolt-action rifle through the ejection port because the ejection port remains unobstructed. Others believe the one-piece design provides additional stiffness to the receiver over the ejection port to support long, heavy barrels.

Whether you choose a one-piece design or a two-piece design may depend on the kind of shooting you will be doing. Shooters who are concerned about receiver stiffness should purchase one-piece bases that attach to the receiver with four screws instead of the normal three screws (two at the front and only one at the back). A one-piece / four-screw base should also be a consideration for rifles with heavy recoil. One-piece "tactical" bases are an example of bases that attach with four screws.

The front base of a two-piece system can be reoriented at its respective position to accommodate a scope with an unusually short main tube. Normally you would orient both bases so the rings will attach as far forward as possible on their respective bases. By reorienting the front base so its ring will attach toward the middle of the receiver you may be able to install a scope with a short tube.

One-piece cross-slot bases provide for installation of scopes with short tubes in a different way. One-piece cross-slot bases have multiple cross-slots at both front and rear positions. Multiple cross-slots on a one-piece base allow rings to be attached at a variety of locations along the rail to accommodate a range of scope lengths.

Both rotating-dovetail and quick-release bases accommodate scopes with unusually short or unusually long main tubes in another way - they accept special rings called extension rings. (Extension rings will be described in part 3 of this series - Selecting Scope Rings).

Scope Bases For Your Rifle

No matter which type of bases you choose or whether you choose a one-piece or two-piece base design, you must select bases that match your model of rifle. Screw hole spacing is the obvious reason scope bases will not mount on any rifle. The screw holes in the bases must align with the screw holes in the receiver.

Another reason is mating surface contours. Not all models of rifles have the same receiver top contour. Bases that match the top of one receiver will not precisely match the top of the receiver of a different model. Some bases fit only one specific model of rifle offered by one manufacturer. Other bases may fit several models offered by a particular manufacturer. Heck, certain bases may even fit several models of rifles offered by different manufacturers. Scope base manufacturers provide tables in their catalogs and on their websites to help you select the correct bases to match your rifle.

If you will order a one-piece base, be sure its length matches the length of your rifle's action. Some bolt-action models are made in two different lengths: short-action (SA) for short and medium length cartridges and long-action (LA) for longer cartridges. The screw holes of a one-piece base for a long-action will not align with the screw holes of an SA receiver. Similarly, the screw holes of a one-piece base for a short-action will not align with the screw holes of an LA receiver. If your rifle has a bolt-action, determine whether or not its model is made in two different lengths. If it is made in different lengths, determine whether yours is a short-action or a long-action (check the rifle owner's manual), then order the correct length of one-piece base. Still not sure? Consider ordering a two-piece base. A two-piece base will fit either length bolt-action. Keep in mind, a one-piece base may not be available for every make and model of rifle.

Steel or Aluminum Bases

Some types of scope bases are made of steel. Rotating-dovetail bases, for instance, are always made of steel. Others types of bases are made of aluminum. A few brands and types are available in both steel and aluminum. Cross-slot and tactical bases are available in both. You must decide between steel or aluminum if the brand and type of base you are interested in is available in both.

Steel or aluminum? Are you more concerned about accuracy or light weight? Steel bases are more resistant to heavy recoil than aluminum bases. A one-piece, steel base will provide more rigidity to help the receiver support a long, heavy, free-floating barrel than an aluminum base. All other factors being equal, steel provides more accuracy than aluminum. But steel bases are more expensive than aluminum bases. And they are heavier. A one-piece steel base is much heavier than a two-piece aluminum base. Order steel bases if you are more concern about accuracy or if your rifle is chambered for a magnum rifle cartridge. Order aluminum bases if you are more concerned about the carrying weight of your rifle.
Finishes

One final decision to make concerning bases is the finish. Scope bases are commonly available with matte black (dull black), gloss black (shiny black), or silver finishes (bare metal). If the finishes of the scope and rifle's receiver are the same, you will probably select bases and rings of the same finish. If the finishes of your scope and rifle's receiver are different, you will probably want bases with the finish that matches the receiver (and rings that match the scope). A finish that matches the receiver gives the appearance that the bases are a part of the receiver (and rings that match the scope give the appearance that the rings are a part of the scope). Or you could choose bases and rings with contrasting finishes. Hey, it's your choice.
CONCLUSION


So, those are some of the considerations in choosing scope bases and some of the options available. You'll choose a base style such as cross-slot rail, rotating-dovetail, quick detach, or other; one-piece or two-piece base; bases to match the receiver contours and length; and a finish that matches (or contrasts) the receiver.

_________________
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I can explain it to you, but I can't understand it for you.

Graffiti in ruins of Pompeii (in the basilica): The one who buggers a fire burns his p....


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 Post subject: Re: How Scopes Work

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SELECTING SCOPE RINGS

A scope mounting system consists of two scope rings and one or two scope bases. Scope bases, as described in the previous article in this series, provide a foundation for the scope rings. Scope rings attach the riflescope to the bases. The rings must mate to the top of the bases, fit the scope, and be the optimum height. Choosing the correct scope rings can be challenging. Selecting the wrong rings is inconvenient; even frustrating. This article has been provided to help you order the correct scope rings - hopefully on the first attempt.

Scope rings are sold separately from scope bases. They are normally sold as a set of two. You will only have to order one set for each scope. You will receive two identical rings if you order a new set of cross-slot (Weaver-type), dual rotating-dovetail, or quick-release scope rings. If you order a set of single rotating-dovetail (Redfield-type) rings, you will get one front ring and one rear ring.

Scope Ring Diameter

Scope ring diameter must match scope main tube diameter

Whether you order ring mounts for integral scope bases or rings for attachable bases, you must order rings of the correct size to match the diameter of the scope tube. Ring are either 3/4-inch, one-inch, 30mm, or 34mm diameter to accommodate either 3/4-inch, one-inch, 30mm, or 34mm diameter scope tubes, respectively. One-inch and 30mm are currently the most common scope tube diameters. The diameter of the scope rings you order must match the scope tube diameter of the scope you intend to mount. Three fourths-inch diameter rings of any brand will fit a three-fourths inch diameter scope tube of any brand. Likewise, one-inch diameter rings of any brand will fit a one-inch diameter scope tube of all brands. And, that's right; 30mm diameter rings of all brands will fit a 30mm diameter scope of any brand. However, a one-inch diameter scope tube will be loose in 30mm rings. And, obviously, a 30mm diameter scope tube would not fit into one-inch diameter rings. (One inch is 25.4mm and 30mm is about 1+3/16 inches.)

Do not confuse the scope objective lens diameter with the scope main tube diameter. Both are listed with the scope specifications and both may be measured in millimeters. But only the scope main tube is enclosed within the scope rings.

Scope Ring Height


Selecting correct ring height is the most difficult decision to make when ordering scope rings. Riflescopes should normally be mounted as low as practical to the rifle receiver. However, the scope on a bolt action rifle must be mounted high enough to allow the bolt handle to be cycled. (Clearing the bolt handle normally will not be a problem with a modern bolt action rifle because modern bolt handles are configured to be operated even with low mounted scopes.) Also, the objective lens bell, with its lens cap installed, must clear the top of the barrel by at least 1/8-inch. The larger the objective lens, the higher the scope must be mounted. More than 3/8-inch scope clearance above the barrel is too much with most rifles.

The length of the scope ring stem determines ring height. Scope ring manufacturers offer rings of different heights to accommodate various scope objective lens bell diameters. Most brands are available in low, medium, and high. Some brands are even offered in extra low or extra high. However, the choices of scope height are a bit confusing because there is no standard method to measure ring height. Some ring manufacturers specify scope height measured from the bottom of the stem where it will contact the base to the bottom of the ring saddle. Other manufacturers measure ring height from the bottom of the stem to where the rings split horizontally. So the scope rings designated as "high" from some manufacturers may actually mount a scope lower than "medium" scope rings from other manufacturers.

But do not only consider scope ring stem length when choosing scope rings. The thickness of the base, the diameter of the scope main tube, and the taper of the rifle barrel also contribute to scope mounting height.
Ring To Base Fit. Cross-slot rings and rotating-dovetail rings will not fit each others bases.

Rings for cross-slot rail bases are not interchangeable with rings for rotating-dovetail bases. That is, cross-slot rings will fit only cross-slot bases while rotating-dovetail rings will fit only rotating-dovetail bases. So if you ordered cross-slot bases you must order cross-slot rings to match. If you chose rotating-dovetail bases you must choose rotating-dovetail rings to match. And dual rotating-dovetail rings will fit only dual dovetail bases.

Obviously, the capacity of rings is different between one-inch and 30mm diameter rings. However, both 1-inch and 30mm rings will attach to the same bases. Therefore, one-inch and 30mm cross-slot rail rings will all attach to the same cross-slot rail bases. And both one-inch and 30mm rotating-dovetail rings will attach to the same rotating-dovetail bases - at least if the rings and bases are from the same manufacturer.

Cross-slot rings of one brand will probably fit cross-slot bases of any brand. Similarly, rotating-dovetail rings from of one brand will probably fit rotating-dovetail bases of any brand. However, to ensure a reliable fit, the bases and rings you order should be the same brand. That does not mean the combination of bases and rings you order has to be the same brand as the scope itself. Provided the brand A ring diameter is the same as brand B scope tube diameter, brand A bases and rings will fit a brand B scope. Besides, not all scope manufacturers make scope mounts anyway.
See-Through Scope Mounts

You may consider see-through scope mounts if you anticipate using sights for close shots and using the scope for farther shots. See-through rings have circular stems that allow a clear view of the sights beneath the scope. However, see-through rings require the scope to be mounted higher than normal to allow a clear view of the sights. You may not be able to get solid cheek contact with the stock for consistent eye alignment with the scope mounted so high.

Some styles of see-through rings require cross-slot bases. Others attach directly to the receiver with screws. See-through rings for .22 rimfire rifles grip the scope mount grooves in the receiver.

Quick-Release Scope Rings

Quick-release rings allow the rings, with the scope installed, to be easily detach and reattach to the bases. Quick-release rings are handy to remove the scope for storing your rifle in a confined gun safe or to prevent scope damage during transportation or maintenance. You should also consider quick-release rings if you plan to switch one scope between multiple rifles frequently. Each of the rifles must have bases that match type of rings installed on the scope. Conversely, several scopes could be exchanged on one rifle like when you carry a spare previously zeroed scope just in case the installed scope is damaged on a remote hunting trip. In this case, each of the scopes must have its own set of rings compatible with the bases installed on the rifle.

There are two types of quick-release systems. With quick-detach rings, the quick-release system is part of the rings. These quick-detach rings fit standard cross-slot bases. No special bases are required. One-half turn of the release lever on each ring loosens its clamp for easy removal from its base. One-half turn of the levers re-tightens the clamps to their bases. The rifle zero must be verified before hunting with this type.

The quick-release levers of the Leupold® QR™ mounting system are part of special bases instead of the rings. The thumb levers are located on the left side of the bases instead of on the rings. These quick quick-release bases will only accept special rings. Rotating the thumb levers forward draws the rings down securely to the bases. Turning the thumb levers rearward releases the rings from the base. Leupold ensures its quick-release system will return the scope to its zero position when reinstalled. The ammunition and time saved from not needing to re-zero should compensate for the higher price.

Tactical Scope Rings

Many competition riflemen prefer tactical rings to secure scopes to their rifles. Tactical rings (sometimes called Picatinny rings) are a bit heftier than standard scope rings and the jaws clamp the base over a wider area. Tactical scope rings provide a larger contact surface around the scope tube. The halves of the rings are secured with either four or six screws instead of the normal two screws. The extra security provided by tactical rings helps to prevent the scope from being knocked off zero. But tactical scope rings on a hunting rifle? Why not? Tactical rings will handle recoil from magnum cartridges better than standard rings. Sure, tactical rings may not be as sleek as standard scope rings. But the extra security provided by tactical rings is desirable on hunting rifles as well as competition rifles - perhaps more desirable. Competition shooters are more careful with their prized rifles in a shooting range environment than most hunters are with their rifles in hunting environments.

Tactical rings

Standard tactical rings will not fit standard cross-slot bases

Both standard cross-slot (Weaver-type) rings and tactical rings will fit tactical bases. However, tactical rings, with a larger cross-screw or thicker recoil tab (0.205"), will not fit the narrower (0.180") cross-slots of standard cross-slot (Weaver-type) bases. Therefore, you can order either tactical rings or standard Weaver-type (cross-slot) rings if you order tactical bases. On the contrary, if you order a standard cross-slot base, you must order standard cross-slot rings to fit or you must order tactical-style rings with narrower cross-screws to fit the slots of standard cross-slot bases. The specifications of tactical rings that will fit standard cross-slot bases usually state those rings will fit Weaver-type bases.
Extension Scope Rings

Perhaps you have realized by now that low power scopes - scopes used by big game and dangerous game hunters - have relatively short main tubes. Often these scopes are mounted on rifles that shoot magnum cartridges. Rifles that shoot magnum cartridges have long receivers to allow the bolt enough travel to feed magnum length cartridges from the magazine. Trying to mount a short scope on such a long receiver could pose a problem. If the scope tube barely spans the distance between the rings, there may not be enough leeway to slide your scope forward or backward to adjust for eye relief.

Short scopes can be mounted on two-piece cross-slot bases by orienting the bases on the receiver so cross-slots and, therefore, the rings will be closer to the middle of the receiver. However, a one-piece cross-slot base cannot be reoriented. It can be attached to the receiver in only one direction. However, one-piece cross-slot bases have several cross-slots to attach the rings at various positions along the length of the base. The rings can be attached at whichever cross-slot positions provide the best eye relief.

Rotating-dovetail bases and Leupold® QR Mounts™ accommodate short scopes a different way. The front base will accept an extension ring to shorten (or lengthen) the span between the rings. The front ring is offset about 5/8-inch longitudinally from the stud that fits the base. Extension rings can be used to reduce the space between the rings 5/8-inch to accept extremely short scopes or turned around to expand the space 5/8-inch to accept long scopes.

Scope Ringmounts


Ringmounts attach to integral scope bases

If your rifle has integral bases and you decide to use those bases without installing additional bases, you must attach rings mounts to the integral bases. Ringmounts are scope rings that attach directly to integral scope bases or rails. The integral bases on a Ruger® 77 rifle accept ringmounts designed for the Ruger® 77 rifles. The integral bases on a Ruger®#1 rifle accept ringmounts designed for the Ruger®#1 rifles. ringmounts designated for CZ receivers will fit only BRNO CZ® integral bases. And ringmounts designed for Sako® rifle receivers will fit Sako® integral bases. Neither cross-slot rings nor rotating-dovetail rings will fit integral bases.

If, in some rare case, you cannot find ringmounts to fit integral bases or if you prefer to have attachable bases on your rifle, you can mount separate bases on top of the integral bases then select rings that will fit the new bases. Integral bases are often drilled and tapped by the manufacturer to accept additional bases for this reason. Other types of attachable bases clamp onto the integral bases.

Twenty-two caliber rimfire rifle receivers usually have two parallel scope mounting grooves. You could use ringmounts specifically designed for .22 rimfire rifles to mount a scope. Neither cross-slot nor rotating-dovetail rings will work there. The space between the parallel grooves on the receiver is either 3/8-inch or 11mm. Select rings with a 3/8-inch wide clamp or 11mm wide clamp to match. Some brands of .22 rimfire ringmounts will fit both 3/8-inch and 11mm spaced grooves on .22 rimfire rifles by turning the moveable clamp jaw over.

If your rifle does not have integral scope bases, you must order scope rings to fit the attachable bases you have selected.

Steel or Aluminum


Just like scope bases, scope rings are made of either steel or aluminum. Some brands and models of scope rings are available in both. Others are available in one or the other.

Should you order steel or aluminum rings? Normally, the material of the rings should be the same as the bases. Order steel rings for steel bases or aluminum rings for aluminum bases. However, you could order aluminum rings for steel bases if suitable steel rings are not available. Aluminum cross-slot rings have steel cross-screws and steel moveable jaws anyway.

Attaching steel rings to aluminum bases is not recommended. All scope bases must resist the inertia of the scope and its rings during recoil. Steel rings, being heavier than aluminum rings, have more inertia that the bases must resist. This additional inertia may cause hard steel ring jaws to wear into softer aluminum bases during heavy recoil causing the rings to loosen.

Surface Finish

The final decision for selecting scope rings is probably the easiest - choosing the surface finish of the scope rings. Most scope ring brands are offered in gloss (shiny) black, matte (dull) black, or silver finish. Most customers order the scope ring finish that matches their scope. This makes the scope and rings appear to be one unit. Some like the rings to contrast with the scope finish. There is nothing wrong with ordering a set of rings that will contrast with the scope finish, unless you are a hunter. Most hunters order matte black rings for a matte black scope to reduce game-frightening glare.

Summary

Since scope rings attach the scope to the bases, they must be compatible with the both the scope bases and the scope. The rings must mate to the bases. Also, be sure to order scope rings that have the capacity to accommodate the main tube diameter of your scope and the height to allow the objective lens bell (with lens cap installed) to clear the top of the gun barrel by just a bit more than 1/8-inch. The scope ring finish is usually a matter of preference.

_________________
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 Post subject: Re: How Scopes Work

Sniper

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CHECK THE RINGS

After the scope bases have been attached to the rifle receiver, the next step to mount a scope is to attach the rings to the bases.

Be certain the scope rings are the correct size and height to accommodate your scope before you install them onto the bases. Scope rings are not be returnable or exchangeable if they have been marred. So do a preliminary check of scope ring height and size before you install the rings to determine whether or not you have the correct rings before you waste time and effort trying to install the wrong rings and risk marring the finish in the process. It will take only a few minutes.

Obviously the ring attachment system must be compatible with the bases installed on the rifle. (e.g., rotating-dovetail rings for rotating-dovetail bases and cross-slot rings for cross-slot bases.) Also, the size of the rings must match the diameter of the scope tube. (1-inch rings for a 1-inch scope tube, 30mm rings for a 30mm scope tube, etc.)

If the rings are the correct size and type, place the rifle in the gun cradle or sight-in vise and open the action. Remove the ring half screws and set both ring caps (the top halves of the rings) aside. Loosen both ring clamp screws completely if they are cross-slot Weaver-type) rings. Remove the lateral screws from the rear base if you have single rotating-dovetail system (Redfield-type). Turn the lever on the left side of the bases rearward if your rifle has quick-release bases. Loosen all the clamp screws if you have ringmounts for integral bases.

Install the lens caps on the scope. Carefully place only the bottom half of the rings on their respective bases. Position cross-slot rings at the most forward cross-slot on their respective bases. Do not tighten the clamp screws on cross-slot rings and do not throw the locking levers on quick-release bases yet. If the stem of one ringmount is longer than the other, the ringmount with the longest stem goes on the rear base. Support the dovetail lug of the front ring of a rotating-dovetail system along the left side of the front base and hold it there with your fingers because it will not stay there by itself. Check ring height and scope clearance.

Carefully place the scope in the rings so you do not knock the ring bottom halves off the bases. Slide the scope forward in the ring saddles as far as the power ring or eyepiece lock ring will allow. Viewing horizontally from either side, does the bottom of the objective lens bell with the lens caps installed appear to be at least 3/16-inch above the top of the rifle barrel or rear sight? The rings are too short if there is not at least 3/16-inch of clearance between the objective lens cap and the rifle barrel (or rear sight). (Later, when you tighten rings, the clearance could be drawn down as close as 1/8-inch. For now, look for at least 3/16-inch of clearance.)

Without disturbing the scope, slowly close and reopen the action. Is the ocular lens bell with its lens cap installed high enough to clear bolt handle if the rifle has a bolt action? Will the ocular bell interfere with the operation of the safety lever? If the rifle has a hammer, can the hammer easily be cocked and decocked? It is better to discover any interference now than after you install the rings.

Order higher rings if the ocular lens cap impedes the operation of the action or if the objective lens cap appears to be less than 3/16-inch above the barrel or rear sight. Higher rings have longer stems to mount the scope higher.

Attach the scope rings to the scope bases only after you determine the rings are the correct size and height. Quick-release, quick-detach, cross-slot rings, and rotating-dovetail rings each attach to their bases differently. Ringmounts attach directly to integral scope bases. Some of the most common scope ring attaching methods are described below.
Quick-Release Rings

Leupold® QR™ (quick-release) rings have a stud under the stem of each ring that is inserted into a special base. A thumb lever located on the base is rotated to lock each ring onto its base. As their name implies, quick-release rings are easy to release from their bases; and they are almost as easy to attach.

According to the previous article in this series, the bases should have been installed with the locking levers on the side opposite the ejection port. Rotate both locking levers rearward. Wipe the ring studs with gun cleaner-degreaser. Orient the rings so the locking grooves in the ring studs are rearward. Insert each of the ring studs into its recess in its base and rotate the locking lever on the side of each base up and forward to draw the rings down and lock them. The rings are attached. Easy, huh?

Quick-Detach Rings

Quick-detach rings are scope rings that clamp to standard cross-slot bases by tightening thumb levers located on the rings themselves. They are almost as easy to attach to their bases initially as they are to detach.

Turn the thumb levers of both quick-detach rings fully counterclockwise to open the jaws. Wipe the cross-screws and the insides surfaces of the ring jaws with a gun cleaner-degreaser patch to remove crud. Also wipe the cross-slot and rails of the bases. Orient both rings so the levers will be on the side opposite the ejection (usually the left side). Place the rear ring in the closest cross-slot behind the ejection port. Turn its thumb lever clockwise to clamp the jaw to the base. The lever may require several turns or as little as 1/2 turn to tighten depending on the brand and style. Place the forward scope ring in the forward-most cross-slot. (If you discover later that the scope tube is too short to span between the rings, you can quickly detach the front ring and reposition it a slot or two rearward.) Tighten its lever by turning counterclockwise also. Lightly tap the fixed jaw side of each ring toward the receiver a few times with a mallet to settle them onto their bases. Then try to turn the thumb levers tighter. If the thumb levers tightened any more, lightly tap the fixed jaw side again and try to re-tighten the levers. With any luck, the levers will be pointed rearward when the jaws are tight so they will be less likely to loosen if snagged on a branch while hunting. The thumb levers of some brands of quick-detach rings such as Warne® Maxima™ rings can be repositioned out of the way after tightening without loosening the jaws.

Cross-Slot Rings & Tactical Rings

Cross-slot rings nuts should be on the opposite side of the ejection port

Cross-slot (Weaver-style) rings, of course, attach to cross-slot bases. Loosen the nuts or screws (whichever your rings have) on the cross-slots and open the clamp jaws. Wipe the cross-slots and the rails of the bases and the cross-screw and inside surfaces of the ring jaws with gun cleaner-degreaser to remove gunk. Position each ring at the forward-most slot on its respective base for now. (You can reposition the front ring a slot or two rearward later if you discover the scope tube does not span between the rings.) Align the cross-screw or the recoil tab with a cross-slot. Whether your rings have nuts or screws, both nuts or both screw heads should be on the same side. Position the nuts on the side of the receiver opposite of the ejection port so the nuts will not interfere with case ejection. (Position the nuts on the left side if your rifle ejects to the right; on the right side if your rifle ejects to the left.) Turn the nut (or screw) on each ring clamp until the rings are tight on the bases. Lightly tap the fixed jaw side of both rings toward the receiver a few times with a mallet to settle them onto their bases. Now tighten each ring to its base just a bit more. (Just a little tighter than snug. Do not over tighten. Over tightening will strip or shear the cross-screws.) Tap the end of the screwdriver or nutdriver with a mallet as you apply light tightening torque. Tap the fixed jaw toward the receiver a few more times and re-tighten the nuts without over tightening them. That is how you attach cross-slot rings.

Ringmounts

Ringmounts attach to integral bases in one of several ways depending on the model of rifle. Some ringmounts have a fixed jaw on one side and a clamping jaw on the other side. Both jaws clamp on another type. A third type of ringmount has a dovetail recess underneath that slides onto an integral dovetail rail on top of the rifle receiver.

No matter which type of ringmounts you have, wipe the integral base recesses or grooves and the ringmount jaws with a cleaning patch wet with gun cleaner-degreaser.

If your ringmounts have one fixed jaw each, loosen the clamping jaw of both ringmounts, orient the ringmounts so both nuts are on the side opposite the ejection port, and insert the fixed jaws into one of the grooves on the receiver. Be certain the fixed jaws are squarely in the grooves or recesses then tighten the clamping jaw of each ringmount. Lightly tap the fixed jaw of both ringmounts toward the receiver with a mallet to settle the jaws into the groove. Try to re-tighten the clamping jaws after you tap the fixed jaws into the grooves. Alternately tap the fixed jaw and tighten the clamping jaw until the clamping jaw will not tighten anymore with light torque.

Ringmounts for Sako® centerfire rifles slide onto integral dovetail rails on top of the receiver. The ringmount with the recoil pin attaches to the rear base and must be slid forward onto its rail from the rear. Loosen the clamping screws and slide each ringmount onto its respective integral base. The clamping screws of both ringmounts should be on the same side. The rear ringmount can only be placed in one location on its rail due to the recoil pin. The forward ringmount should be placed about 1/4-inch behind the forward end of the front integral base for now. You may have to slide it rearward later to accommodate a scope with a short main tube later. Tighten the clamping screws to secure each ringmount to its base. The ringmount with the longer stem goes on the rear integral base.

Ringmounts that fit Ruger® rifles have clamping jaws on both sides and a recoil tab under the stem. Tighten both jaws of each ringmount completely before you try to put the ringmounts on the bases. Now evenly loosen each jaw one turn at a time alternating between sides until you can just slip ringmounts onto the integral bases. If one ringmount has a longer stem than the other, the ringmount with the longer stem attaches to the rear integral base. Be certain the recoil tab of each ringmount goes into its recess. Now tighten the jaws 1/2-turn at a time alternating between sides while holding the ringmount in position. Alternate 1/4-turns when the jaws become snug. Tap the ringmounts stems lightly from side to side with a mallet to settle them. Then try to re-tighten the each jaw no more than 1/8-turn before tightening the other side. Tap the ringmount stems from side to side then attempt to re-tighten the ring jaws.

Rotating-Dovetail Rings

Attach the rear ring first if you will be installing a dual rotating-dovetail system. If you are installing a single rotating-dovetail (Redfield-style) ring, install the front ring first. Do not use the scope to turn rotating-dovetail rings into position. The ring will have considerable resistance to rotation which may damage the scope. Instead, use a 1-inch scope ring lapping bar or a 1-inch wooden dowel to turn 1-inch diameter rings. Use a 30mm scope ring lapping bar to turn 30mm diameter rings. Loosen the ring cap screws just enough to slip one end of scope ring lapping bar or dowel through so it protrudes about 1/4-inch out the other side. Tighten the ring cap screws to grip the bar. Use a ring lapping bar or 1" dowel to turn rotating-dovetail rings.

Apply gun grease to the sloped surfaces of the dovetail lug and to the bottom of the ring stem. Insert the dovetail lug into the dovetail recess. (Remember, if you are installing a dual dovetail mounting system, install the rear ring first.) The bar or dowel should be perpendicular to the rifle and base at this point. Now, hold the rifle down with one hand and swing the bar 90 degrees so it is aligned over the receiver and barrel. Considerable resistance is normal. Swing the bar an additional 15 degrees or so past the barrel and receiver. Then swing it back over the receiver and barrel. Align the bar precisely over the receiver and barrel. Loosen the ring cap screws and slide the bar from the ring. Wipe excess grease from the top of the base.

Attach the front ring the same way if you are installing a dual rotating-dovetail mounting system. After both rings are installed, span the rings with the ring lapping bar and tighten the rings around the bar. Tap both sides of bar near each ring with a mallet several times to align the rings with the lapping bar. re-tighten the ring cap screws and tap both sides of the rings again. Continue to tapping the bar with a mallet then re-tightening the ring cap screws until the screws will not tighten more. The rings will be in lateral alignment when the ring cap screws will not tighten any more. Remove the ring caps and remove the lapping bar.

Attach the rear ring now if you are installing a single rotating-dovetail system. Loosen the cap screws of both rings. (The front ring should already be attached to its base as described two paragraphs above.) Loosen both laterally opposing windage screws of the rear base. Place the bottom of the rear ring stem flat on the top of the rear base. Span the bottom halves of the rings with the lapping bar. Tighten the front ring around the bar first. Slide the rear ring forward or backward on its base until the crescent-shaped recesses in the ring stem are aligned with the windage screws. Turn the windage screws until the screw heads lightly engage the recesses in the stem. Be certain the bottom of the rear ring stem is flat against the top of the rear base then tighten the rear ring around the lapping bar. Snug both windage screw heads to the rear ring stem. Center the rear ring on top of the base by first loosening one screw and tightening the other. Remove the ring caps and remove the lapping bar after the rear ring is centered and the windage screws are tight.

That was how to install scope rings onto the bases. Now you can install the scope into the rings.

_________________
SI VIS PACEM, PARABELLUM

I can explain it to you, but I can't understand it for you.

Graffiti in ruins of Pompeii (in the basilica): The one who buggers a fire burns his p....


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 Post subject: Re: How Scopes Work

Sniper

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Check Scope Tube Fit

Remove the screws that hold the ring caps on the ring saddles. Set the caps aside so you will know which cap mates with whichever saddle later. Place the scope in the scope ring saddles. Does the scope tube fit into the saddles of the scope rings? A 30mm tube will not fit into 1-inch rings and a 1-inch tube will be too loose in 30mm rings.

Will the scope span the distance between the scope rings? If scope does not span the distance and the bases are cross-slot tactical bases, remove the front ring and reinstall it at a different cross-slot. Slide the front ring rearward so there will be at least a 1/8-inch space between the front ring and the objective lens bell if the front base is a dovetail rail. Replace the front ring of a rotating dovetail system with an extension ring if the scope tube will not span between the rings.

Check Ring Alignment

The bores of the scope rings must be aligned with each other both vertically and laterally. Tightening the scope ring top halves (the caps) around a scope seated in either vertically or laterally misaligned rings will cause the scope to bend. The scope will twist if the scope rings are tightened in rings that are both vertically and laterally misaligned. Scope internal mechanisms are assembled with such close tolerance that bending or twisting the main tube will stress the delicate lenses, springs, and screws inside the scope causing malfunction or permanent damage. Severe ring misalignment could scratch or kink the main tube, distort the seals, crack the lenses, interfere with the windage and elevation adjustments, and damage the power changing mechanism. Do not damage your riflescope with misaligned rings.

Some brands and types of scope rings include alignment inserts that pivot universally within the rings. The inserts bear on the scope main tube and pivot within the rings to compensate for slight ring misalignment rather than bending or twisting the scope tube to the rings.

If your scope rings do not include pivoting inserts, ring alignment is easy to check with a set of scope ring alignment bars or rods. Use 1-inch bars to align 1-inch rings and 30mm bars to align 30mm rings. One bar is installed in each of the rings with the pointed ends toward the middle. Ring alignment is indicated when the points are aligned. You'll be able to determine lateral alignment by looking straight down from above. Rotating dovetail rings can be rotated or windage screws turned to correct lateral misalignment. Vertical alignment is determined by viewing relationship of the points horizontally. Vertical misalignment of more than 1/16-inch can be corrected by inserting a shim of the correct thickness under the low base of a two-piece base and a bit of scope ring lapping. (Do not fret; correctly installed scope bases and rings rarely have more than 1/16-inch of misalignment.) Vertical misalignment of less than 1/16th-inch can be corrected by lapping the scope rings. (That is no more than 1/32-inch of lapping required per ring.) Do not lap the scope rings into alignment yet; you must be certain the rings are compatible with your rifle and scope before you lap them. (Scope rings are not returnable after they have been lapped.) Ring height is one more factor that must be certain.

Ring height affects the objective bell clearance above the barrel and the clearance of the bolt handle below the ocular bell on bolt-action rifles. The scope's longitudinal position within the rings will also affect scope clearance because the eyepiece and the objective lens bell are at opposite ends of the scope. Because eye relief is adjusted by sliding the scope forward or backward in the rings, you must adjust eye relief before you can be certain ring height is adequate. Adjust eye relief now.

Adjust Eye Relief

Eye relief is the distance from the ocular lens: a viewer's eye must be to see the full field of view (FOV). You must adjust eye relief to fit yourself. Read How To Adjust Eye Relief Correctly on this website for more information about eye relief and how to adjust it.

Be sure the objective lens end is toward the muzzle. Since you should set eye relief close to its forward limit, position the scope as far forward in the saddles (the bottom half of the scope rings) as power adjustment ring or the eyepiece lock ring will allow. Place the ring caps (the top half of the scope rings) over the scope tube and install the screws. Do not tighten the screws because you must slide the scope rearward within the rings to adjust eye relief.

Will you be wearing heavy clothing when you hunt? Will you be wearing a recoil pad? The thickness of your coat will affect eye relief. So will a recoil pad. Put the heaviest clothing on to adjust eye relief that you will be wearing when you go shooting.

Remove the lens caps. Set the power at its highest magnification if the scope has variable-power. The highest power setting will provide the shortest eye relief range. You can adjust eye relief for the lowest power setting later if you have a variable power scope. Do not be concerned with focusing or leveling the reticle yet.

With the rifle unloaded and on 'SAFE', pick up the rifle, point it at a light-colored featureless wall, close your eyes, and assume your shooting position. You must adjust the eye relief to fit you; do not adjust you to fit the eye relief. So do not crane or scrunch your neck. Just assume a comfortable shooting position.

Relax. Now, maintaining that comfortable shooting position, establish a good stockweld. Now you can open your aiming eye. Do not change your head position. Attempt to view through the scope. What do you see? Do you see the whole field of view clearly the instant you open your aiming eye or do you see a shadow around the perimeter?

Slide the scope 1/8-inch or so rearward (toward you). Close your eyes, assume your preferred shooting position again, relax, and get a good stockweld. Without changing your head position, open your aiming eye. Do you see any perimeter shadow now? If you still see shadow, move the scope another 1/8-inch rearward. Continue sliding the scope rearward in 1/8-inch increments and checking until you do not see any perimeter shadow - none at all. Close your eyes each time before you establish a stockweld so your are not tempted to crane or scrunch your neck. Check the eye relief at least three times but as many you need to be certain there is no shadow.

When the scope is at a position where there is no perimeter shadow, slide it rearward one additional 1/8-inch. At this position the scope should be about 1/8-inch within the forward limit of the eye relief range. Check the eye relief again at this final position. You should not see any shadow now. Wrap two strips of electrical tape around the scope tube

Eye relief is adjusted if you do not see any shadow. Careful; do not move the scope. Put the lens caps on. Remove the ring half screws and the ring caps being careful not to disturb the scope. Leave the scope in the ring saddles. Cut two strips of 1/2-inch wide electrical tape; each 3+1/8-inch long if your scope has a 1-inch main tube or each 3+5/8-inch long if your scope has a 30mm tube. (Black electrical tape goes well with a scope that has a black surface finish. White electrical tape looks better on scopes that have a silver finish.) Stick one end of each strip of tape on the scope main tube precisely where each of the ring saddles is located. Pick up the scope and wrap each strip of tape all the way around. The tape will mark the eye relief position.

Place the scope back into the ring saddles. Align the electrical tape strips with the rings. Place the scope ring caps in position and install the screws. Do not reinstall the ring caps yet; you still have to be certain the rings are the correct height for your scope and rifle.

Check Ring Height scope clearance

The objective lens bell with lens cap installed should clear the barrel by 1/8 to 3/8-inch

Check ring height again now that you have adjusted eye relief. The lens caps should have been re-installed already. Press the scope tube down to the bottom of the ring saddles with hand pressure. Operate the action. Check if the bolt handle will clear the ocular lens bell if it is a bolt action. If the action has a hammer, be sure it can be cocked and decocked without striking the ocular lens bell. Be sure the safety lever can be operated without if it has a thumb-operated safety lever.

Now check the clearance between the objective lens bell and the top of the barrel again. With the rings securely attached to the bases, the clearance should be at least 1/8-inch with the lens caps installed. It is better to be a just bit more than 1/8-inch than any less. However, the clearance between the objective lens cap and barrel should not be more than 3/8-inch. If your rifle has a rear sight and the scope extends to the rear sight, the scope with lens caps installed must clear the rear sight by at least 1/8-inch also.

You must exchange the rings for some with longer stems if the objective lens cap clearance above the barrel is not at least 1/8-inch. That is why you should not have lapped the rings into alignment yet.

Thread Locking Compound (?)

By now you should know whether or not the scope rings are compatible with your rifle, bases, and scope. Would you like to permanently attach your bases to the receiver? Thread locking compound will prevent the screws from loosening - even if you wanted them to loosen. You will have difficulty removing the bases if you ever wanted to try a different scope base style. Do you really want your scope bases to be permanently attached to your rifle? Then remove the rings and bases and go through the process of reinstalling them after you apply a drop of thread locking compound to each scope base screw. (Apply thread locking compound to the scope base screws only. Do not apply thread locking compound to any of the ring screws.) You could do all that if you really wanted to or you could simply be confident that you have installed the bases correctly so far.

Lap The Rings


Lap the scope rings to correct slight misalignment

Scope rings should conform to the scope rather than forcing the scope to conform to misaligned rings. Vertical ring misalignment less than 1/16-inch can be corrected by lapping. Even if the rings are in alignment, lapping will increase ring bearing surface on the scope tube and remove burrs from the rings that might scratch the scope finish.

Do not lap scope rings that include alignment inserts; let the insert serve their intended purpose. The inserts will pivot to align with the scope tube despite the rings being misaligned themselves.

If scope rings without alignment inserts are misaligned, a scope lapping bar of the correct diameter - a 1-inch bar for 1-inch rings or a 30mm bar for 30mm rings - is required to lap scope rings into alignment. Lapping compound is applied to both ring saddles and the lapping bar is spanned across both rings. Then bar is pressed and rolled into the lapping compound. The pressure points within the scope rings will wear away because the ring metal (aluminum or soft steel) is softer than the lapping bar. Scope ring lapping takes some effort, but when it is finished the rings will be in nearly perfect alignment. Follow the instructions included with the scope ring lapping kit.
Install The Ring Caps

Remove the lapping bar and thoroughly clean the lapping compound from the rings with gun degreaser. Align the electrical tape around the scope tube with the ring saddles and place the scope back into the ring saddles. The tape will keep the rings from scratching the scope finish and will help the rings grip the tube so leave the tape strips around the scope tubes unless the tape interferes with the fit of the rings around the scope. The elevation (up and down adjustment) turret must be on top with the windage (left and right) turret on the right side. Place the ring caps over the scope tube. Be sure to return the ring caps to their original saddles. Degrease the screws and just start them into the rings. Do not tighten the ring cap screws yet. You may have to rotate the scope within the rings to level the reticle before you tighten the ring screws.

Level The Reticle

The vertical crosshair must be vertical and directly over the rifle bore for accurate shooting. In other words, the reticle must be level. So how can you level the reticle? One method is to turn the power down to its lowest magnification, view a door frame or window frame through the scope, and align the vertical crosshair with the frame. That works assuming you are actually holding the rifle level as you viewed the door frame. You may not realize you are canting the rifle.

Using a Level-Level-Level™ to level a scope reticle

Another method it to hang a carpenter's level horizontally on a 100 yard target frame at a shooting range and align the horizontal crosshair with it. This method works only if you were not canting the rifle as you aligned the horizontal crosshair of the scope with the level.

Wouldn't it be nice to have some sort of device to indicate the rifle itself was actually level before you leveled the reticle to that rifle - one you could magnetically attach to your rifle? Well, if you have a Wheeler Engineering® Professional Scope Mounting Kit™ you have such a device. It is include with the kit. It is called the Level-Level-Level. (The Wheeler Engineering® Level-Level-Level™ can be purchased separately or as part of the Professional Scope Mounting Kit.) It actually includes two bubble levels. The first one really does magnetically attach to the rifle. The second level is placed atop the elevation turret after the rifle has been leveled with the first one. Without disturbing the rifle, the scope can then be twisted within the scope rings to center the bubble of the second level. The horizontal crosshair of the scope reticle is level when the bubble of the second level is centered.

Final Ring Cap Tightening

The taped sections of the scope tube are aligned with the rings. The ring caps are on their respective ring saddles. The screws are started and the reticle is level. You are almost done! All you have to do is tighten the rings around the scope main tube.
The space between the ring halves should be equal on both sides
The space between the ring halves should be equal on both sides

Do not use thread locking compound on the ring half screws. It is not needed there. Tighten the rear scope ring half screws first. You have to tighten the left and right screws of the ring half evenly. The reticle may cant if you do not tighten the screws evenly. You can alternately turn the left and right screws one full turn initially. Alternately tighten the screws only 1/4-turn when you feel the screws start to tighten. The torque of the left and right screws should feel about the same if you do this right. Do not overtighten the screws. Just a bit more than snug. You do not want to shear the screws off. The rings halves should tighten around the scope tube before they tighten to each other. Do not tighten the ring caps so much that they collapse the scope tube. You should see a small space between the ring halves of horizontally-split rings. The spaces between the top and bottom halves should be about the same on the left and right sides. The left and right sides of the ring have not tightened evenly if the spaces are not about the same or if one side of the ring has closed completely. Tightening the rings unevenly may cause the scope to rotate and cant the reticle. You will have to loosen both screws completely, re-level the reticle, and tighten the screws evenly.

Assuming you tightened the rear scope ring halves evenly, you should verify the levelness of the reticle before you tighten the front ring half screws.

Is the reticle still level? Tighten the front ring half screws that same way you tightened the back ring half screws - evenly. Recheck reticle level. You are done if the reticle is still level.

That is how you mount a scope! See, it is not difficult. It just takes some time to do correctly.

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 Post subject: Re: How Scopes Work

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When To Sight-In A Riflescope

Obviously you must zero after you install a new scope. Also, your scope may need to be re-zeroed occasionally. Occasions that require re-zeroing or at least zero verification are after the scope or mounting system is reinstalled, after your rifle has been reassembled, the action has been reinstalled into the stock, before hunting, after the rifle has been dropped or the scope bumped, a change of brand or bullet type of ammunition, after severe atmospheric condition changes, after an unexplained miss, or whenever zero is in doubt.

Getting Ready

Get ready to go to the shooting range and sight-in your rifle. There are several things you should do before you head to the range.

You should clean the rifle bore before you sight-in. Clean the bore thoroughly if you have not cleaned the bore recently. Whether you have cleaned the bore recently or not, run a dry cleaning patch through the bore to absorb any residual solvent or oil and be certain the bore is not obstructed.

Check the trigger guard screws or action screws. Tighten them if needed. Check the scope mount screws also.

Is the eye relief distance of your scope adjusted correctly? Incorrectly adjusted eye relief is not only annoying - it can be dangerous if recoil drives the scope into your eye. Do not wait til you shoot your rifle to discover the eye relief distance is too short; check and adjust it before you shoot to be safe. See 'How To Correctly Adjust Eye Relief' on this website to read about the correct way to adjust eye relief.

Do not forget to check the levelness of the reticle after you have adjusted eye relief and before you tighten the scope ring screws. The reticle should be level with the rifle before you sight the scope to the rifle. Reticle cant will cause aiming errors at any range closer or farther than the distance you sighted in.

You can check the focus of the scope reticle at home or you can do it at the shooting range. In any case, the reticle should be focused before you boresight and sight-in your scope. The scope must be focused by you and for you. Wear the same eyeglasses to focus the reticle you will use to sight-in if you wear glasses. Check the current focus setting before you mess with it; it may already be adjusted for you. Do not view the reticle for longer than two seconds. Do the focus check at least three times to be certain. Do not change the focus setting if the reticle was clear the instant you view through the scope. Focus the reticle if it was not clear. Detailed information about reticle focusing is included on the How To Focus A Reticle page.

If you have an optical boresighting tool such as a collimator, you can get boresighting out of the way before you go to the range. An optical boresighter attaches to the muzzle of the rifle either magnetically or with the appropriate size bore arbor. Follow the instructions of your particular boresighting tool. The instructions explain how to align the reticle with the grid pattern in the collimator. Boresighting merely aligns the reticle with the rifle bore. Boresighting does not sight-in the rifle. Since boresighting makes no allowance for muzzle jump, barrel whip, bullet drop, and precession, you still must go to the range to sight-in. However, boresighting will save time and ammunition when do sight-in. When you get to the shooting range the first boresighted shot will probably be much closer to the aim point than if you just when to range and started shooting and wondering where your bullets are going. Boresight Before You Sight-In has more information about boresighting.

You will need:
Ruler
Marker
Pencils
A Nickel
Ammunition
Masking Tape
Sight-In Targets
Shooting Glasses
Hearing Protection

Do you have everything you will need to zero your rifle? Targets, ammunition, hearing protection. . . What are you forgetting? See the Rifle Range Kit page on this website for a list of items you should consider taking.
Get some Free, Printable 100-Yard Rifle Scope Sight In Target form the web or on this address:

http://www.about-shooting.com/Sight-In_Targets.php

Be sure to sight-in with the same type of ammunition you will use to hunt. That means same brand, bullet type, and same bullet weight. Hunt with ammunition from the same lot as you zeroed with if you have it. (If the ammunition lot number is not stamped somewhere on the outside of the carton, it may be on the inside of one of the flaps.) Buy or reload enough ammunition before you go to the shooting range to both sight-in and hunt. Use those left over odd rounds of a different brand, bullet type, and bullet weight to practice your shooting technique after you sight-in.

Do you know how far you will be sighting in? How high should you sight-in at 100 yards to achieve your desired sight-in range? Visit the Trajectory Tables page on this website to discover your ammunition's trajectory before you go to the range. Do you need sight-in targets? Check out Print A Sight-In Target to print the appropriate sight-in target for your ammunition's trajectory.

Most scopes have windage and elevation click values of 1/4-inch per 100 yards. That is 1/4-inch per 100 yards. Not 1/4-inch at all ranges. Click values will be different at ranges other than 100 yards. What will the click values be at the distance you will be zeroing for? The Click Value Table on this website shows the click value at various ranges. Print one to take with you.

How is the weather? Do not let an adverse weather system interrupt your range session. You will need time to zero your rifle correctly. Also, it is difficult to zero when the wind is blowing. Zeroing when the wind is blowing will result in a false zero. Attempting to zero when the wind is gusting is frustrating. Therefore, you should zero when the wind is calm. The wind is most likely to be calm early in the morning and late evening. However, evening means it will be getting dark soon. Early morning is usually the best time to zero a rifle for several reasons - daylight is increasing, wind is normally calm, and mirage is less intense.

At The Rifle Range

Laser boresighting and visual boresighting should be done at the range. Twenty-five yards is the best range to boresight because the bullet will cross the your line-of-sight (LOS) at about 25 yards on its way to the target at whatever reasonable distance you sight-in. So claim a shooting bench shooting bench with an unobstructed view of a 25-yard target frame as soon as you get to the shooting range.

Why should you boresight? Two good reasons to boresight are to save time and to save ammunition. Boresighting helps to get your first shot, when you finally take it, somewhere - anywhere - on the target. You'll have an idea how to adjust if your first shot hits somewhere on your target. There is no use in walking a sight-in target way out at your intended final zero range then discovering that your first bullet missed the whole darn target. Maybe you will get lucky and hit the target with your first shot. Maybe. Don't count on it. How many shots will you shoot just to get on paper? Better just boresight. 'Boresight Before You Sight-In' has more information about boresighting.

Reset the dial scales to "0" after each adjustment

Turn the scope magnification to its lowest power setting if it has variable-power. Adjust the parallax to 25 yards or as close as you can to 25 yards if your scope has parallax adjustment. Install your laser boresighter and point it at the 25-yard target or remove the bolt if you have a bolt action rifle and view the target through the bore after you post a target at 25 yards. Stabilize the rifle, remove the scope turret caps, place a penny or nickel in the coin slot on the windage dial (the dial on the right side of the scope), and adjust the vertical crosshair into alignment with the laser spot on the 25-yard target or, if you are boresighting visually, adjust the vertical crosshair to the middle of the target as viewed through the bore. Adjust the horizontal crosshair with the elevation dial (the dial on top) second. Most riflescopes have click adjustments based on a distance of 100 yards. You must adjust four times as many clicks to center the reticle on the laser spot or boresight target at 25 yards. Refer to the Click Value Table. Turn the laser boresighter off and remove it after you adjust the reticle to the laser spot or reinstall the bolt if you boresighted visually through a bolt-action.

Hold the windage dial with a coin so it does not turn, loosen the screw that secures the windage scale (if the scale is secured by a screw), align the "0" on the scale with the index mark on the windage turret, then retighten the screw that secure the scale. Do the same with the elevation scale. Reinstall the turret caps.

First-Shot

Be sure the range is clear. If range rules allow, you may as well take your first shot at the 25-yard boresight target since you already have a target posted there anyway. Besides, the bullet will cross the LOS at about 25 yards on its way to the sight-in target at whatever reasonable distance you decide to sight-in. This shot can also be your fouling shot to remove any residual oil or solvent you missed with your dry cleaning patch earlier. (Be warned: the rules of some rifles ranges prohibit shooting a centerfire rifle at a target less than 50 yards away. That makes no sense because muzzle blast for any particular rifle will be the same whether you aim at a target 25, 50, 100-yards, or whatever distance away. The bullet has to pass through 25 yards on its way to a 50-yard or beyond target anyway. Do not violate the range rules. Place a sight-in target at the minimum distance allowed and start from there.)

Use the same type of ammunition you will use to hunt. Aim as carefully at the center of the boresight target as you would at a sight-in target at 100 yards or beyond. Take your time. Do not let yourself be distracted. Apply the fundamentals of accurate shooting - stable position, steady rest, natural point-of-aim, good sight picture, breath control, gentle trigger squeeze, and follow-through. Shoot only when you are ready.

Did your shot hit where you aimed? Probably not. Boresighting does not take barrel whip, parallax, wind drift, and a few other factors into account. But if you boresighted correctly, the bullet hole will be somewhere on the target. When the range is cold ("cold" means no one is shooting or ready to shoot), use a ruler to measure the distance the center of the bullet hole is from the vertical line. Measure how far the center of the bullet hole is from the horizontal line separately. Write both these two distances on your notepad. The arrows on the scope elevation and windage dials indicate the correct directions to turn to move the bullet point-of-impact (POI) to the point-of-aim (POA) you used, so adjust accordingly. Remember, the click values are worth only 1/4th at 25 yards what they are at 100 yards. For example, 1/4-MOA (about 1/4-inch) clicks at 100 yards move the POI only 1/16-inch at 25 yards. If you are not sure you measured and adjusted correctly, fire another shot at the 25-yard boresight target and readjust. Reset the windage and elevation scales to "0".

Retrieve your 25-yard boresight target if your are certain that you measured and adjusted correctly.

Sighting-In

Post a sight-in target at 100 yards. You could first sight-in directly at 100 yards then subsequently adjust the POI the appropriate height above the POA needed to sight-in at the desired range. Or you could simply sight-in the appropriate distance high at 100 yards from the start. (Visit the Trajectory Tables page before you go to the shooting range and select a trajectory table to see the recommended sight-in range for your ammunition and the estimated trajectory at 100 yards. The following instructions pertain to the sight-in targets available on the 'Print A Sight-In Target' page, so print a 100-yard sight-in target that matches your ammunition's trajectory at 100 yards. Print a duplicate target while you are at it to keep at the shooting bench with you for reference.)

Turn your scope's power to its highest setting if it has variable power and adjust parallax to 100 yards if it has a parallax adjustment. Adjust the shooting bench, rest, and rifle to you. If you will hunt with a bipod or a support sling, use it to sight-in also. When the range is clear, load one round of the same type of ammunition you will hunt with, assume a stable shooting position, and aim directly at the point-of-aim on the sight-in target. Apply the fundamentals of accurate shooting. Take your time. Fire just one shot. Try to make it your best shot.

Do not make any scope adjustments yet. How did the shot feel? Did you do everything right? Admit to yourself if you messed up; no one else has to know. Simply consider that shot a practice shot if you messed it up. You are still sighting-in, so do not expect to hit your intended POI on the target yet. If that shot was not acceptable you, either walk downrange and tape over the bullet hole or, if you can see it on the target through your spotting scope, plot its position on the duplicate target you kept at the bench and "X" it out so you remember to disregard it. Wait at least three minutes to let the barrel cool then make the next shot better.

If the first shot (or a subsequent shot) felt good, consider it your first sight-in shot. When the range is cold, walk downrange with your notepad, duplicate target, pencil, marker, and ruler. First, draw a circle around the bullet hole with the marker so you can see it better back at the firing line. Next, measure how far the center of the bullet hole is left or right of the middle vertical line. Round the measurement to the nearest 1/4-inch (or round to the nearest 1/2-inch if your scope has 1/2-inch click values or 1/8-inch if it has 1/8-inch clicks). Then measure how far the bullet hole is above or below the horizontal line that bisects the impact circle. Round that measurement also. Either write both of these measurements on the notepad so you do not forget them by the time you get back to your shooting bench or simply plot the bullet hole on the duplicate target. Designate the horizontal measurement with a left or right arrow to indicate which direction you must make the scope adjustment to move the POI and designate the vertical measurement with an up or down arrow. (Alternatively, you can view the target from the firing line with a spotting scope, plot the bullet hole on the duplicate target, and take the measurements there. The sight-in targets available on the Print A Sight-In Target page have parallel lines spaced 1/4-inch apart to help measure and plot bullet holes.)

Adjusting The Scope


Back at the shooting bench, calculate the scope adjustments required to move the POI to the center of the impact circle.Simply count the number of 1/4-inches (or 1/2-inches or 1/8-inches depending on the click values of your scope) the center of the bullet hole was left or right of the middle vertical line on the target. Verify that you did reset the dial scale to "0" so you can return to it if you miscount the clicks. (Hint: If the wind was blowing from the left or right when you fired the 100-yard shot, leave the windage dial where it was after you adjust previously for the 25-yard shot. The windage you adjusted at 25 yards is probably closer to correct than the windage at 100 yards because the wind drifted the bullet much more at 100 yards than it did at 25 yards. Of course, if the wind was not blowing from the left or right, adjust the windage for 100 yards.) Turn the windage dial that number of clicks. The arrows on the dials indicate the correct direction to move the POI. Refer to dial images printed on the duplicate target if the scope dials or target knobs do not have arrows. Reset the dial scale to "0". Then adjust the elevation to the center of the impact circle in the same manner.

By now the barrel should be cool. Realistically, you will be shooting your first shot at game from a cold rifle barrel, so sight-in with a cold barrel as well. Let the barrel cool at least three minutes between shots and at least five minute between shot groups.

Do not assume the first shot was ideal and your scope adjustments were perfect. The scope click values are not always precise 1/4-inch or 1/8-inch or whatever at 100 yards, so fire the next shot to verify the scope adjustments you just made. Aim more carefully than you did previously. (Always try to make each shot your best shot.) Use the same POA as you did for the previous sight-in shot. Fire just one shot again.

Did this shot land within the large impact circle on the target? It probably did if you fired this and the previous shot carefully and you made the correct scope adjustments (and the click values are precisely as indicated). Measure the bullet hole distance from the center of the impact circle and readjust the scope accordingly if that shot did not land within the large circle.

Estimating MPI


Estimating the mean point-of-impact of a shot group

If the shot did land within the large circle, fire two more good shots to form a shot group, allowing the barrel to cool at least three minutes between shots. This is not a competition, so you can disregard any shots you believe you messed up and fire another. Plot the shot group on your duplicate target considering only your good shots and disregarding any bad shots or go downrange to measure the group when the range is cold. If your shot group is not centered in the impact circle, you must adjust it.

Another Method to Sight-In

This other method, often called the "One-Shot Sight-In" method, involves adjusting the reticle to the bullet hole instead adjusting the point-of-impact to the reticle. It requires you to be able see a bullet hole with your scope at 100 yards

After boresighting at 25 yards, ensure both dial scales on the scope have been reset to "0", aim at a target posted at 100 yards, and fire only one good shot. If you cannot easily distinguish the bullet hole through your scope or if you intend to eventually sight-in to a distance beyond 100 yards, walk downrange when the range is cold and draw a small circle around the bullet hole with a black marker. If you intend to sight-in to a range beyond 100 yards, draw and fill in a second circle to make a dot about 1/2-inch in diameter centered the same distance directly below the bullet hole as the trajectory would be above the line-of-sight (LOS) for whatever final range you intend to sight-in. Measure and note the horizontal and vertical distances of the center of the dot - or the center of the bullet hole if the final sight-in range will actually be 100 yards - from the point-of-aim (POA) you used to fire the shot.

Back at the shooting bench, place the unloaded rifle in a sight-in vise, aim at the same POA you used to fire the shot, and tighten the vise so the reticle remains fixed on the POA when you let go. Carefully step away from the rifle so you do not disturb it. Round both the measurements you made at the target to the nearest scope click value and, standing next to the shooting bench while touching only the scope dials so you do not disturb the rifle, make the appropriate windage and elevation adjustments on the scope. Normally the scope adjustments move the POI to the reticle. However, because you are trying to adjust the reticle to the bullet hole or dot you drew on the target, the scope adjustments work in reverse of what is indicated by the arrows on the dials. (For example, turning the dial "UP" moves the reticle down and turning the dial "LEFT" moves the reticle right.) Turn the dial back to "0" if you get confused or lose count of clicks. If you disturb the rifle, turn both dials back to "0", aim the reticle at the POA again, and start the over click adjustments over.

View through the scope after you make the scope adjustments without disturbing the rifle. The reticle will be on or close to the dot (or the bullet hole if your final sight-in range is 100 yards) if you made the correct scope adjustments. Without disturbing or touching the rifle so you do not have the urge to aim at the dot, make the remaining few scope adjustments required to move the reticle to the dot while viewing through the scope. Reset the dial scales to "0" after you adjust the reticle to the dot.

Okay, now you can disturb the rifle. Remove the rifle from the sight-in vise, aim at the POA on the target, and shoot a 3-shot group to verify your attempt to sight-in with only one shot.

Adjusting a shot group is a bit different than adjusting a single bullet hole. Tape over or "X" out the bad shots and draw lines with a marker to connect the three good shots you accept as your shot group. A shot group rarely forms a perfect geometric shape. Unless the lines draw a unilateral triangle, you must determine the mean point-of-impact (MPI) of that group and adjust MPI to the center of the impact circle. The MPI is not the center of the group unless connecting the three bullet holes form an equilateral triangle. You could take time to measure, calculate, and plot the MPI precisely but that will be not necessary because you will round it to the nearest click adjustment value later anyway. So just estimate. Imagine a vertical line about 2 inches long half way between the two bullet holes with the least lateral space between them. Estimate 2/3 of the distance between the farthest laterally displaced bullet hole and the vertical line. Draw vertical pencil line about 2 inches long there. Similarly, imagine a horizontal line half way between two bullet holes with the least vertical dispersion between them. It may be the same two bullet holes for some shot groups. Estimate 2/3 of the distance between the farthest vertically displaced bullet hole and the vertical line. Draw a horizontal pencil line about 2 inches long there. The estimate MPI is where the two pencil lines cross. Now measure the lateral distance of the MPI from the center of the impact circle of the target then measure the vertical distance. Jot down both measurements so you do forget them. Replace the target if you believe you will have trouble distinguishing any new bullet holes from the current holes. Change the scope windage and elevation adjustments accordingly back at the bench. Reset the dial scales to "0" after you complete the adjustments.

Fire another good 3-shot group after the barrel has cooled for at least five minutes. Allow the barrel to cool at least three minutes between shots. The MPI of this group should be near the center of the impact circle. If not, readjust the scope windage and elevation dials as required, reset the dial scales, and shoot another group. Do not forget to reinstall the scope turret caps after you have sighted in.
Beyond 100 Yards

Your will be scope zeroed to 100 yards (or to shoot the appropriate distance high at 100 yards for a more distant sight-in range). Does your shooting range extend all the way out to your desired sight-in distance? If it does, you should post a target out there, fire a shot-group, then make scope adjustments if needed. Do not be too concerned if your shot group is a bit larger at the farther range. That is normal. However, it should be centered around the point-of-aim (POA) at that range unless the wind is blowing, in which case the windage dial should still be where it was after you shot at 25 yards. Refer to the Click Value Table for the click values at that range if you must make scope adjustments.

Do you have some odd rounds of a different type of ammunition that remain from an earlier range session or previous hunting season? Use them to practice your shooting technique after you sight-in. But do not change the scope dial settings for the odd ammunition. Leave the dials set for the ammunition you used to zero. You are only practicing your shooting technique. It is okay if the bullets do not hit where you aim. Your scope should still be zeroed for the ammunition you will hunt with which is what this range session is all about.

Some sight-in sessions at the rifle range are better than others. But a bad day at the range is still better than a good day at work. May your next sight-in session be your best!

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 Post subject: Re: How Scopes Work

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@atiqmassan, Sir, You "complete" this thread.
:text-thankyouyellow:

Now please suggest me a right "Scope" to read this all. :geek:

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 Post subject: Re: How Scopes Work

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Mian Jee.. i Just followed the lead.. The way it is posted on a website (in my first post detailing everything) it is with photos that are embedded. If you follow the link you will see a LOT of nice pics and pictorial method.
Lovely find.. for all the brothers.

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Atiq bhi and Mian g both did a great,I think it is more than sufficient for an occasional scope user like me


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 Post subject: Re: How Scopes Work

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Excellent share Atiq bhai. Very useful.

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