Optics terms and information

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Ftaview

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Terms:

Adjustable Objective
An adjustable objective is a dial around the objective end of the scope, or a knob on the left side of the turret housing that allows you to adjust your scope's parallax to a certain distance by moving these adjustments until a clear picture is perceived, and/or the marked corresponding incremental yardages are approximated to your target distance. The correct setting of an adjustable objective prevents the apparent movement between the reticle and the target when the shooter moves his head slightly off center of the rifle scope.
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Airgun Scope:
Airgun scopes are specially designed to withstand the dual-recoil of spring piston airguns. Powerful spring piston airgun recoil will destroy non-airgun rated scopes in short order. Airgun scopes are often sealed on both sides of the lenses and made more strongly overall. They also have adjustable objectives to allow the shooter to use high magnification at short distances. Official airgun distances are 10 meters (33 feet), 25 feet, and 50 feet.
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Coatings:
Microscopic coatings on the lens surfaces reduce light loss and glare due to reflection. Coated lenses offer a brighter, higher contrast image with less eyestrain. More coatings allow better light transmission, but it is very possible to have a scope with a single coating to greatly outperform a scope with multicoated lenses. It all depends on the quality of the coatings as well as the glass. Good quality does not come cheap. The following are accepted terms for coatings:

* Coated: A single layer on at least one lens surface.
* Fully Coated: A single layer on all air to glass surfaces.
* Multicoated: Multiple layers on at least one lens surface.
* Fully Multicoated: Multiple layers on all air to glass surfaces.

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Click:
A click is one adjustment notch on the windage or elevation turret of a scope. One click most often changes a scope's point of impact 1/4 inch at 100 yards. Some clicks are 1/8 inch, 1/2 inch, one inch, or even more.
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Exit Pupil:
An exit pupil is the small circle (column) of light that is visible in the ocular lens when you hold your scope (or binocular) at arm's length. The larger the exit pupil is, the brighter the image that will be entering your eye. To find the exit pupil for your scope, divide the objective lens diameter in millimeters by the magnification. For example, if your scope is four power (4X), and your objective lens is thirty-six millimeters in diameter (36mm), divide 4 into 36 and it equals 9. Nine would be the exit pupil size in diameter in millimeters.
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Eye Relief:
Eye relief is the distance your eye must be from the ocular lens and still get a full field of view.
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Field of View:
Field of view (FOV) is the amount of area seen through your scope from right to left at 100 yards. As magnification is increased, FOV is lessened. As magnification is decreased, FOV is increased. For example, a typical 3X variable scope might have a FOV at 100 yards of a bit over 30 feet, and at 9X, the FOV would be around 14 feet. A larger objective lens will not change these figures.
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Hold Over/Under:
Hold over/under is the amount of point of aim change either above or below your target, without adjusting your scope, to adjust for the trajectory of your projectile.
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Kentucky Windage:
Kentucky windage is the amount of point of aim change either left or right of your target, without adjusting your scope, to adjust for wind effects on your projectile.
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Magnification:
Magnification is the power rating of the scope, indicated by the symbol "X". A 10X (ten power) scope makes objects seem ten times closer than with the naked eye.
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Maximum Point Blank Range:
The longest distance you can hold dead center in your kill zone and not be too high or too low for a hit in the vital area. Flatter trajectories and/or larger targets increase this range.
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Minute of Angle:
Minute of Angle (MOA) is a unit of measurement of a circle, and is 1.0472 inches at 100 yards. For all practical purposes it is called 1 inch at 100 yards. It is 2 inches at 200 yards, 5 inches at 500 yards, one half inch at 50 yards, etcetera.
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Objective Lens:
The objective lens is the lens closest to the object being viewed. It is measured in millimeters in diameter. A larger objective lens allows more light to enter the scope. In a three to nine by forty (3-9X40) scope, the 40 is the objective lens size.
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Ocular Lens:
The ocular lens is the lens closest to your eye.
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Parallax:
Parallax is the apparent position of the reticle on the target image at different ranges. This is most visible when the eye is moved outside the center of a scope while viewing a target at other than the standard distance at which the scope has been preset to be parallax free. Most riflescopes without adjustable objectives are set at 100 or 150 yards. Rimfire scopes are often set at 50 or 60 yards, and shotgun scopes are often set at 60 or 75 yards.
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Power:
The power of the scope is the same as magnification. A 10X (ten power) scope magnifies ten times, and makes the object appear ten times closer than with the naked eye.
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Resolution:
Resolution is the measurement of an optical device's ability to produce a sharp image by distinguishing fine detail. Resolution is determined by the quality of the glass and coatings, precision manufacturing, atmospheric conditions, and visual acuity of the user.
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Reticle:
A reticle is a system of lines, dots, or crosshairs in your scope that appear superimposed on your target.
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Trajectory:
Trajectory is the flight of your projectile after it leaves the barrel. This flight is an arc. The amount of arc depends on the projectile weight and velocity.
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Turret:
A turret is one of two knobs in the outside center part of the scope tube. They are marked in increments, and are used to adjust elevation and windage for points of impact change. These knobs protrude from the turret housing.
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Twilight Factor:
Twilight factor is the measurement of the efficiency of a rifle scope in low light conditions. The higher the twilight factor, the more useable the scope is in twilight conditions. The formula for determining twilight factor is: The square root of magnification times the diameter of the objective lens. Coatings and glass quality are not represented in this figure.
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Zero:
Zero is the distance that you are sighted in at, and references the flight of the projectile. If you are sighted in at 200 yards, you have a 200 yard zero.
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Reticle focal plane:
Typical internal construction of a scope with its reticle in the First Focal Plane.

The reticle may be located at the front or rear focal plane (First Focal Plane (FFP) or Second Focal Plane (SFP)) of the telescopic sight. On fixed power telescopic sights there is no significant difference, but on variable power telescopic sights the front plane reticle remains at a constant size compared to the target, while rear plane reticles remain a constant size to the user as the target image grows and shrinks. Front focal plane reticles are slightly more durable, but most American users prefer that the reticle remains constant as the image changes size, so nearly all modern American variable power telescopic sights are rear focal plane designs. European high end optics manufacturers often leave the customer the choice between a FFP or SFP mounted reticle.

Variable power telescopic sights with front focal plane reticles have no problems with point of impact shifts. Variable power telescopic sights with rear focal plane reticles can have slight point of impact shifts through their magnification range caused by the positioning of the reticle in the mechanical zoom mechanism in the rear part of the telescopic sight. Normally these impact shifts are insignificant but make accuracy oriented users, that wish to use their telescopic sight trouble-free at several magnification levels, often opt for front focal plane reticles. Around the year 2005 Zeiss[9] was the first high end European telescopic sight manufacturer who brought out variable magnification military grade telescopic sight models with rear focal plane mounted reticles. They get around impermissible impact shifts for these sights by laboriously hand adjusting every military grade telescopic sight. The American high end telescopic sight manufacturer U.S. Optics Inc.[10] also offers variable magnification military grade telescopic sight models with rear focal plane mounted reticles.

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How to Choose a Riflescope

How to Choose a Riflescope

These days, most firearm enthusiasts use some kind of optical sighting device on most of their guns. Not just rifles, but shotguns and handguns as well.

There's a great reason for this. Simplicity. Aiming through a scope or a red dot sight completely eliminates one third of the complexity of lining up iron sights. With metallic sights you are required to line up the rear sight with the front sight and your target. With a scope, you simply have to line up your crosshairs (reticle) with your target. It's much easier to learn to shoot with a scope than iron sights, and since most rifle scopes also magnify, your target appears closer, and therefore easier to see, enabling you to place a more precise shot on your target. People with less than perfect vision are able to adjust the eyepiece (ocular) focus for their particular eyes for a clear, crisp sight picture. Older eyes often have a difficult, if not impossible time trying to switch their focus from a rear sight to a front sight to a target as required without a scope, and it's frustrating to say the least. Scopes eliminate this frustration.


The Right Tool for the Job

You don't use a seven ounce claw hammer to pound in sixteen penny nails, or a baby sledge hammer for finishing nails.

Magnumitis sinks its ugly claws into greater numbers of hunters every year. Cartridges and scopes get more powerful annually, and uninformed nimrods often use these combinations for whitetail deer where almost all shots are well under a hundred yards. Bullets go faster and optics magnify more because they sell. Manufacturers will make anything they think enough people want. Pink scopes? Start a petition. Square main tubes? Have enough people phone. This is fine. Some people might call this progress. But use the right tool for the job.

The average deer rifle used to wear a 3-9 scope, and for good reason. Three power is low enough, with enough light transmission and field of view for close shots in most applications, and nine power gives you plenty of magnification for longer shots. A major percentage of people now want to choose scopes for whitetail deer with top magnifications of fourteen, or twenty, or even more. This is, more often than not, a mistake. Less is more.

Not only does higher magnification subtract from your available light, the low end of a high magnification scope is much too high to take a very close shot. Your scope on a whitetail rifle should almost always be kept at its lowest power. If that power happens to be five or six, many times your deer, only yards away, appears as a hairy patch through your scope, or your field of view is so narrow you can't find him, or it's so dark you can't make him out.

The first question a Navy aircraft carrier pilot asks about a new jet aircraft is not how fast it goes, but how slow it goes. They have to land on a tiny moving piece of flight deck bobbing around on an immense ocean. Slow is more important than fast in most cases.

Just as those bold Navy pilots, it's prudent to know how low a scope goes, not how high. Low is more important in most cases. You can always shoot far with low power, or have time to turn your scope up, but you can't shoot close with high power because your field of view (FOV) is too small and light transmission is poor.

I might be getting ahead of some folks with my descriptions. The following diagram might help a bit.


rifle-diagram.gif



In a 3-9X40 scope, the 3 means three power, or 3X. This means that the image you see through the scope appears three times (3X) closer than it does with your naked eye. The 9 means nine power, or nine times (9X) closer than it appears with your naked eye. The forty (40) is the objective lens diameter in millimeters. This is a variable scope because you can vary the magnification of the scope from three to nine, stopping anywhere in between. You would describe this scope as a "three to nine by forty."

Most scopes, especially in America have main tubes that are one inch in diameter. That means that they use one inch rings. Some scopes have thirty millimeter main tubes. Those scopes will use thirty millimeter rings. There are several main types of bases that are used to connect the rings to your firearm. You need to know what kind of base you have to find out the exact type and height of the one inch or thirty millimeter rings you will use for your specific scope.


Light Transmission and Eye Relief

Scopes don't gather light, as most people think, although the term "light gathering ability" has become accepted jargon. Scopes transmit available light through the lenses to your eye, always losing a bit in the process. The best a scope can hope to offer in light transmission is about a theoretical 98%, which only the very finest (read expensive) scopes can hope to approach. Anything above 95% is considered great, and most scopes are around 90%, give or take a bit.

The more magnification you have, the less light you get to your eyepiece. The larger the objective lens, the more you get through your eyepiece.

Aged eyes may dilate to only about four millimeters. Younger eyes may open up to seven millimeters and even more.

The small circle of light that appears in the eyepiece when you hold a scope at arms length is called an exit pupil. Here's an interesting experiment to help explain it. Take a variable scope, put it at its lowest power, and hold it at arms length. See the circle of light in the ocular lens? That is the exit pupil. The diameter of it in millimeters is the exit pupil size. Now turn the scope up to its highest power and try it again. See how much smaller it gets? Imagine if you are using this scope during poor lighting conditions as common in hunting situations, like dawn or dusk. How small and dark will that exit pupil be? How well do you think you'll be able to see through that tiny circle of light?

A formula for exit pupil is as follows: Divide the objective lens size in millimeters by the magnification. Example: if your 3-9X40 scope is set at 3X, 40 divided by 3 equals 13.3 millimeters, which is large enough for almost all low light applications. If your scope is set at 9X, 40 divided by 9 equals 4.44millimeters. The difference in available light from the larger exit pupil is significant.

The larger the exit pupil, the less critical the position of your head in relation to the scope is, also. The distance that your eye must be to the ocular lens to get a full, clear picture is called eye relief. Lower powered scopes will have a larger range of distance available for a full view. Higher powered scopes are sometimes very critical in relation to the centering of your eye through the middle of the tube, and the distance your eye must be from the ocular lens. Sometimes there is only a half inch closer or further you may be to see the whole available view. The largest eye relief currently available is about five inches, and that is pretty rare. Four inches is still great, and most scopes are between three and three and a half inches. Higher recoiling guns including slug guns require lots of eye relief to prevent "scope eye" or the cut that some people get from the ocular lens of the scope coming back under recoil and cutting a semicircular gash above the shooter's eye.

When mounting a scope, it should be at its highest power, and in a position that your head and neck are comfortable. Your head should be positioned on the stock in the position you will be shooting the most. For instance, if you sight in a gun while shooting off a bench rest, your head tends to sneak up on the stock a bit. If this gun is then used for snap shooting for deer in the woods, your eye relief might not be optimal, nor might your sight picture.


Choosing a Magnification Range

As we have already discussed, a scope in the 3-9 magnification range for a whitetail deer gun is pretty standard. In Western states for mule deer or antelope, a 4-12 or 4.5-14 is not too much, especially when your average shot is many times as long as it would be in the eastern whitetail woods. On the plains or in open country you can even leave your scope at a higher power. You can often see all around you, with little chance of an animal surprising you, which they seem to do occasionally, anyway. In some cases you might have to shoot from hilltop to hilltop, or mountain to mountain.

For prairie dogs or long range target shooting, a 6-20X or 8-25X variable scope does not have too much power. Keep in mind though, on hot days, mirage and heat waves can make a high power scope almost unusable.

Some people prefer fixed power scopes for their simplicity and fewer moving parts. On some rifles, People like nothing more than a fixed 4X. Squirrel rifles and many 22s are well equipped with this magnification. Some target shooters use fixed power scopes with high magnification such as 24, 36, or 40 power.

A 2X scope is the most common for a handgun in a magnified scope. The more magnification you have, the harder it is to find your sight picture and target, and the more critical and closer your eye relief becomes. Shooting a handgun with a scope requires lots of practice, especially with anything over 2X. Higher powered variable scopes are really for the experienced shooter and are used almost exclusively from a rested position.

Shotgun scopes and muzzle loaders often have low power scopes for short range deer hunting with slugs, and for turkey. Again, a fixed 2X is fairly standard, but the trend is for variable power 2-7 scopes or even 3-9 scopes. Parallax is often factory set at 50, 60, or 75 yards. Shotgun scopes generally have maximum available eye relief to prevent "scope eye."


Parallax

Parallax is hard for most people to understand. One way to help explain it is to picture the following: Most riflescopes in a medium-high variable power range, say 10X or slightly higher, which often don't have external parallax adjustments, are parallax corrected at either 100 or 150 yards. If you take one of these scopes that is set at 100 yards and put it in a vise on high power, with the crosshairs centered on a bullseye on a target at say, 25 yards, and move your head slightly off center to the left and right or up or down, you'll see the crosshairs move off the bullseye, even though the scope has not moved. The scope's "eye" is not focused at the proper distance. This will also happen if the target is set at a much further distance, say 300 yards.

Another way to look at it is like this: Put a small mark from a pencil on a table, and put an inch or so of water in a clear drinking glass. Hold the glass an inch over the mark and move it around slightly in different directions. Looking down into the glass, watch the dot move in directions other than where it should be.

External parallax adjustments, called adjustable objectives, are generally on scopes of more than 10 power, or on scopes that are used at close distances. Parallax adjustments are made at the objective lens with a rotating dial marked in incremental distances. Recently it has become popular to install parallax adjustment dials on the left side of the turret housing, which is much more convenient and user friendly. This will become even more common.

Airgun scopes sometimes have high power of 18 or more, even for 10 meter targets. A bad parallax setting will not only appear out of focus, but will wreak havoc on your group sizes, even though your shooting might be technically perfect.

Just because you get a clear sight picture doesn't mean you are parallax free.

A customer asked me the other day if he could get a clear picture through a 2X handgun scope at the 12 foot distance he shoots his air pistol in his house. I went into our warehouse and checked out several different brands. The answer was yes, a clear picture, but by nodding my head even slightly, the crosshairs moved inches off my target. These scopes would be practically unusable at that distance.

If a person only looked directly through the center of their scopes the same every time, parallax would not be an issue, but only a robot could be that repeatable, not a human.

Remember, adjustable objectives are generally not needed for hunting scopes under 10 or even a bit more power. It's just an unnecessary feature to get in your way, and another thing to think about. Keep it simple. The slightly different points of impact possible in hunting applications make the usefulness of this feature negligible.

Airgun scopes and higher power scopes almost always have adjustable objectives. Rimfire scopes are often set at 60 yards for parallax. Shotgun scopes often at 75 yards. Riflescopes mostly at 100 or 150 yards.


Objective Lens size and Tube Diameter

Let's talk about objective lens sizes. 40 to 44mm is pretty standard on a medium variable rifle scope. It's trendy these days to have large objective lenses of 50, 56, or even 75mm in some cases. In most cases, these are unwarranted, and the largest ones are laughable. Large objective lenses will only transmit more useable light than smaller ones if they are set at their highest power in the dimmest conditions. The detriment is comfort and ease of eye alignment. With a properly mounted scope, you should be able to close your eyes, shoulder your gun with a proper, repeatable stock weld (a stock weld is the firm but comfortable and repeatable position of your face on the gun stock), open your eyes, and look directly through the center of your scope every time. Large objective lenses prevent this from happening because of the ring height required to keep such a large lens off your gun barrel. Some scopes require such high mounting that only your chin touches the stock. These scopes are also heavier, clumsier, unwieldy, unbalanced to carry, slower and less comfortable to shoot. Some of these scopes weigh up to an unbelievable 3.5 pounds!

Leupold might have something going on with their new VX-L line of scopes that combine a large objective lens with a contoured bottom that doesn't interfere with your gun barrel, and lets you mount up to a 56mm lens with low rings!

The larger 30mm main tubes on some tubes are most useful for allowing for a greater range of elevation adjustments, not greater light transmission. In fact, most 30mm scopes have the same size lenses that are in one inch tubes.


Lenses and Coatings

Most scopes are fogproof and waterproof. Most scopes have coated lenses. The coatings are expensive and vary in type, number, and quality. It is very possible to have a scope with single coated lenses to greatly outperform a scope with multicoated lenses. It all depends on the quality of the glass and the coatings. Good quality does not come cheap.

The following are accepted terms for coatings:

* Coated: A single layer on at least one lens surface.
* Fully Coated: A single layer on all air to glass surfaces.
* Multicoated: Multiple layers on at least one lens surface.
* Fully Multicoated: Multiple layers on all air to glass surfaces.

Coatings reduce glare, and loss of light due to reflection. More coatings normally lead to better light transmission and sharper contrast.


Field of View

Field of view (FOV) is measured in feet at 100 yards. This is the amount of view you see through your scope from right to left at that distance. As magnification is increased, FOV goes down. As magnification is decreased, FOV goes up. For instance, a typical 3X variable scope might have a FOV at 100 yards of a bit over 30 feet, and at 9X, the FOV would be around 14 feet. A larger objective lens diameter will not change these figures.


Red Dot Sights

Red dot sights are normally 1X. That is to say, they have no magnification. One power (1X) is what our unaided eyes see. These red dot sights offer maximum available light transmission and wide fields of view. They are considered the fastest sights for target acquisition on any firearm. There is also unlimited eye relief on red dot sights. You can mount them on rifles, shotguns, or even handguns. High grade red dot sights such as made by EOTech and Aimpoint are parallax free, brutally strong, and battery life can be up to 50,000 hours! This is not a misprint! Thousands of our soldiers have these sights mounted on their guns overseas, and rely on them to help them protect our great country! Inexpensive red dot sights, although often not waterproof or parallax free are favorites on competition handguns for speed shooting, and on shotguns for turkey and deer. Dot sizes differ from small to large, and some have different reticles available with the turn of a dial. They are generally not for precision shooting because the size of the dot often takes up a good deal of your target at longer ranges.


Anything Called Tactical

Another trend today is the sale of anything called "tactical." Military semi automatic rifles in the hands of advertisement-gobbling civilians often have super-high magnifications on their scopes up to and even including a ridiculous 40 power scope with an absurd 75mm objective lens weighing in at several pounds.

Real military snipers use top quality fixed 10X scopes most often. These have mildot reticles, that in the hands of a practiced individual or team of two, often with calculators, and knowing the approximate size of their target, can estimate distance and hold-over or elevation clicks. Almost all mildot calculations must be made with scopes at their highest power. Fixed power scopes eliminate miscalculations by having a scope set at less than its highest power.

The "mil" in mildot does not mean military. It means milliradian, a unit of measurement for angles.

Stateside law enforcement agencys most often use variable scopes of the highest quality, and mildot type reticles are not often used. They clutter the field of view, and the longest shots almost ever taken are across a street, well under 100 yards. Range estimation is not required.

Mildot reticles in most people's scopes are nothing but a gimmick and an added expense. They will never use them the way they were designed, which is fine. You can still use them in the field to more accurately estimate hold-over at distances, especially for prairie dogs or plinking, or just because you want it. Buy what you like for any reason. You don't have to buy or not buy something because of someone else's opinion.

To get to know how mildots are used as intended, go to this excellent Leupold website and study. Leupold Mil-Dot Instruction Manual

http://www2.leupold.com/resources/downloads/2011_Tactical Milling_Reticle.pdf


mil-dot.jpg




Repeatability

Good quality scopes are repeatable. That is, if you adjust your windage and elevation dials for point of impact at one setting, then move them around and shoot in different places, often in a square grid, then back to the original place, the point of impact will be the same as it was when you started.

Good quality scopes will also move the point of impact when you adjust your dials, without having to "settle in." That is to say, if you move your elevation dial up three inches, your point of impact should immediately reflect that. Sadly to say, more often than not, lesser quality scopes won't do this without shooting a few times first, to "settle in" the scope's internal adjustments. Some people "tap" on their scope with a coin or cartridge case to help this process.


Turret Adjustments and Minute of Angle (MOA)

Adjustments are made in "Minutes of Angle" (MOA). This is a unit of measurement of a circle, and is 1.0472 at 100 yards. For all practical purposes it is called 1 inch at 100 yards. It is 2 inches at 200 yards, 5 inches at 500 yards, one half inch at 50 yards, etcetera.

Scope adjustments are most often made in 1/4 inch increments at 100 yards. Each "click" of an elevation or windage turret will move your point of impact 1/4 inch at 100 yards. That same 1/4 inch click will move your point of impact 1/2 of an inch at 200 yards, or 1/8 inch at 50 yards. Some scopes have clicks that are 1/2 inch or even 1 inch. Some adjustment dials don't have clicks at all, just a friction type adjustment that is infinitely adjustable.

If your bullet hole is four inches low at 100 yards and you have a scope with 1/4 minute clicks, you need to adjust your dial in the direction of the "up" arrow on your turret 16 clicks.

The turrets are housed in the center of your scope tube in a protrusion called the turret housing. The turrets are sometimes made to be turned with a coin, and sometimes they are finger adjustable. Target turrets are tall, and the clicks are easily seen and felt. Target turrets are most suited to use where they won't get banged around or snagged on gear or brush. This is why hunting scopes don't have them, and instead are much lower profile.

The turret caps are often sealed with an "O" ring, and help prevent moisture and debris entering the scope through its weakest parts.


Bullet Drop Compensators (BDCs)

Bullet drop compensators are turret adjustments matched to your caliber and bullet weight. Most bullet drop compensators are matched to common military calibers and weights such as 62 grain 5.56 (.223), and 168 grain 7.62 (.308). They work by having you estimate the range to your target, and by turning your turret to the corresponding distance marked on it. Ideally, your point of impact will be right on. BEWARE! THIS WILL NEVER HAPPEN! Most are substantially off. Even if a BDC was made for a particular load from a particular gun, it still wouldn't be perfect because of other variables. Temperature, elevation, humidity, barrel cleanliness, lot number of ammo, etcetera. Minor changes make big differences. The further the distance, the further off you'll be. Most BDCs for most guns are way off and can be used only to get you close.


Sighting In

If your scope is correctly mounted, using a boresighter should get you close enough to print a bullet hole on a large target at 50 yards. No boresighter, even a laser boresighter, will sight in your gun for you. You must shoot the gun and adjust your scope accordingly to sight it in. Every gun is an individual. No two are alike, even if the serial numbers are consecutive. If a particular gun shoots a certain kind of ammunition well, there's absolutely no guarantee that an identical gun will like it at all.

If you mount a good scope on a good gun with good rings and bases, and find a certain kind of ammo that it shoots well, with a bullet that serves your purposes well, YOU WIN! Buy a case of the same exact ammo with the same lot number, keep it with the gun and don't change a thing.

Also, your scope is at its strongest when your windage and elevation adjustments are in the center of the available adjustment range. When you buy a scope, turn the dials all the way one way and then the other, counting how many full and partial turns, then split that number and find the middle. Start there for your adjustments. Many rear bases have windage adjustments. Use them.


What to Spend

I would rather have a great scope than a great gun. Your gun will work when you pull the trigger, but if you can't see where to place the bullet, the gun is useless. If you can't rely on bullet placement, why even hunt or target shoot? I'll never understand how people can take a week or more vacation, spend $1000.00 on a rifle, and sometimes thousands on a hunt, and buy a $150.00 scope mounted on $20.00 rings and bases. I know of many ruined hunts, and countless dollars lost, and guns wrapped around trees because of a faulty scope. I would rather spend $500.00 on a gun and $500.00 on a scope in good rings and bases, and lots of ammo and trigger time getting to intimately know my gun. During hunting situations, you often have enough to think about, including concealment, scent, and often at high elevations, just breathing. You shouldn't have to think about having to work your gun.

Spend as much as you can afford on your new rifle scope, and less on the firearm or something else if you have to, but get good glass you can count on, and learn how to use it well. Use a rangefinder if you want, but for long shots, you should know your bullet's trajectory and be confident that you can place all your shots in the vital area of your quarry every time. Good glass makes it easier for success.
 
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Introduction to Importance of a Secure Scope Mounting System

Introduction to Importance of a Secure Scope Mounting System

The weakest link in a shooting system is your scope mount. The finest rifle and scope combination is rendered useless without rugged and reliable rings and bases. Often, a problem is not foreseen and results in a miss, or even worse, a wounded animal. Countless rounds have been wasted due to the improper installation of rings and bases, and the frustration that results from missed easy targets takes the fun out of informal plinking and target shooting.

Poor base and ring installation may result in more than bad accuracy. It can destroy scopes and damage rifle receivers and bolts, and can even be dangerous to the shooter. Having a gunsmith install these critical links between your gun and scope is always a good idea, and the peace of mind from a professional installation is well worth the small fee. Do-it-yourselfers often end up spending the saved money anyway on ammo in a fruitless and expensive effort sighting in. This aggravating process is more like work than pleasure. Remember, shooting is supposed to be an enjoyable activity.

An ideal mounting system secures your optical device to your firearm as low as comfortably possible, with the fewest parts necessary. More parts equal more chances for something to go wrong. Solid steel mounts are the strongest, but in many cases, aluminum will serve perfectly well. See through rings are notoriously weak, and points of impact change from bumps or carrying are common. With a good scope with low enough minimum magnification; your iron sights will never be used.


The following are some of the most common mounting systems.

Weaver Style

The most common scope mounting system is called a Weaver style. These utilize the flat rails with crosswise slots in them that you see on everything from rifles to shotguns to handguns. The Weaver style bases are 7/8 inch wide and accept Weaver style rings. Most manufacturers make Weaver style rings. There are crosswise protruding rails, a type of recoil lug, running underneath the rings that fit into the corresponding crosswise slots in the Weaver bases. This prevents movement fore and aft under recoil and abuse. The bases may be one or two pieces and be made of steel or aluminum. Weaver rings are detachable from their bases with the scope still in them, and can be reattached without a major loss of zero. The scope can be reinstalled on a different gun, or removed for gun maintenance or travel. Swapping scopes for different purposes is also facilitated.

Picatinny / MIL-STD-1913

Picatinny rails are similar to Weaver rails (bases), and have a standardization first published by the Picatinny arsenal in 1913. The major difference between Weaver rails and Picatinny rails are the width of the crosswise cuts in them. Picatinny bases have wider slots. The recoil lugs under picatinny rings are thicker to correspond to the wider slots in picatinny bases. Therefore, Weaver rings will fit on picatinny bases, but picatinny rings won't fit on Weaver bases. This is how it's supposed to work, but Weaver style base manufacturers have been cutting thicker slots in their bases to accommodate picatinny rings, and picatinny ring manufacturers have started to put smaller recoil lugs on their rings. The instances of an actual picatinny specification ring not fitting on any Weaver style or picatinny rail are few, and not something to be overly concerned about unless we're talking about the very best mil-spec equipment. Some Picatinny rings are tightened with a torque wrench to a certain number of inch-pounds for repeatability.

22 Rings / Tip-off Rings / 3/8" Dovetail Rings

3/8" dovetail rings are normally used on grooved receivers. Grooved receivers have cuts running lengthwise in the of the gun deep enough for the claws of the rings to firmly grip on. Grooved receivers are normally found on 22 rifles and airguns (although some European 22s and air rifles have grooves that are 11mm or 13mm). Sometimes there is actually a 3/8" base screwed onto the receiver instead of grooves cut into it, often because of lack of metal thickness of the receiver.

These 3/8" rings may have a circular diameter to hold a scope with a main tube of 30mm, one inch, 7/8", 3/4", or others. A standard 22 ring might be called a "one inch tip-off", or a "one inch 22 ring", or a "one inch 3/8" dovetail ring".

Some grooved receiver 22s are drilled and tapped for Weaver style bases. It is prudent to use these much larger bases if available. Weaver style bases simply offer more area for the rings to grab.

Redfield / Leupold Style

The Redfield / Leupold style of bases and rings are a standard that non-weaver mounting systems are measured by. They can be one or two pieces, and are steel, sleek, and strong. They are reliable and trouble free. There is almost as much interchangeability between manufacturers with these systems as there is with the Weaver style. Unlike Weaver style rings, Redfield / Leupold style rings are not detachable. The half of the rings must be separated to remove your scope.

The front ring is kind of a press fit, with a protruding, beveled rectangle of metal under the ring, turned tightly into a corresponding dovetail slot in the front base. Normally, the two halves of the ring are loosely assembled, and a scope ring tool or a one inch wooden dowel or a screwdriver handle is inserted between the pieces to gain leverage to turn the ring into the base. This can not be done by hand.

The rear ring sits flush against the base and is held there by two opposing screws tightened into it. The screws have a leading edge that fit into corresponding slots in the ring. The base screws are tightened into each other, squeezing the ring tightly and immovably. By backing out one screw and tightening the other, the ring moves laterally on the base, effectively acting as a windage adjustment. This is of minimal importance unless your base screws are tapped into your gun's receiver crooked, or there is some other problem that makes your gun shoot left or right so much that it can't be easily corrected with minor scope adjustments.

Dual Dovetails (DD) Systems

Dual dovetail bases are the same as Redfield / Leupold style, but instead of the windage screws holding the rear ring to the base, they are omitted, and instead, the rear ring is turned in, just like the front. This does not offer the extra windage adjustments that the standard bases offer, but it is hardly ever of major importance, and the trade-off of a more securely installed ring is certainly worth the trade.

Clamp-on Mounts

Clamp on mount such as made by B-Square and other manufacturers allow easy scope mounting on guns that aren't drilled and tapped for scope mounts. They do not require gunsmithing, and are easily removed without harm. Older handguns and shotguns often utilize these mounts, making it a much more useful and fun firearm that can be shot more accurately.


Ring Height (According to the 2006 Leupold Catalog)

"50mm riflescopes will almost always use HIGH rings in a given style. In certain instances, such as with extremely heave barrels or some makes of firearm, SUPER HIGH rings may be necessary."

"42-45mm riflescopes will almost always use MEDIUM rings in a given style. In certain instances, 45mm scopes may require HIGH rings."

"40mm riflescopes will almost always have enough clearance with LOW rings in a given style, though MEDIUM rings will give slightly more clearance, particularly when using a barrel with a thicker shank portion or a heavier contour."

"28-36mm riflescopes will almost always use LOW rings in a given style. Again, in certain instances of a heavy barrel or heavy shank portion of a custom barrel, MEDUIM rings may have to be used, but LOW rings will almost always suffice."

"20mm riflescopes will almost always be able to use LOW rings, but in some cases may also use SUPER LOW rings. In this instance, bolt handle clearance of the OCULAR bell will come into play more so than objective / barrel clearance and should be carefully considered."


Points To Remember

Your ring halves are supposed to have gaps between them. Don't try to make them close. Just make the gaps even.

You can easily lap your rings by putting a small amount of jeweler's rouge or Flitz on a metal bar the same diameter as your scope tube and rubbing the coated bar in your installed rings to smooth out the burrs. Be extremely careful to remove all traces of this mild abrasive, and take caution not to get any rouge on any firearm part. When you are done, you can see the shiny places where the high spots were. This gives a more secure purchase for the rings to do their job, and firmly hold the scope.

Shimming bases is easy. Cut shim stock from a steel or aluminum can slightly smaller than the size of the base, and punch holes where the screws will go. Raising a base will give elevation that does not require your scope to be too far off center, its strongest point.

The more you remove and install turn-in rings, the looser they get.

When snapping the tight fitting halves of rings over your scope, insert a dollar bill between the pieces to prevent scratching the scope. The bill is then easily removed.

Remember, your scope mount is the weakest link in your shooting system.
 
Done and got rid of unrelated posts.

Please keep this post for scope information only guys so we can keep it an informative sticky with not allot of junk.

Or, we can always lock it ;)
 
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Lots of good info there .... Thanks

I have some info (a few pages) saved on mildot style scopes ,range estimation etc. It is too much to try and post here but if anyone wants it send me a pm with your e-mail address and I will send it to you .
 
Brownells has a article on this https://www.brownells.com/.aspx/lid=10816/guntechdetail/Torque_Specifications_for_Gunsmiths

Another tip for sights the correct loctite for the screw locking is 222 as used by the British Army REME it's a very low strength loctite Designed for small screws and can be found in most bolt supply stores. Using the thread locker from your automotive store will be too strong and you risk damaging the screws holding the rings on.
 
Can anybody confirm, when a scope manufacturer lists the eye relief, the number is at maximum zoom? E.g. if 4" eye relief for 3-9x scope, is the 4" at 9x zoom? And more eye relief if at 3x zoom?
 
jermyzy said:
Can anybody confirm, when a scope manufacturer lists the eye relief, the number is at maximum zoom? E.g. if 4" eye relief for 3-9x scope, is the 4" at 9x zoom? And more eye relief if at 3x zoom?
Click to expand...

I would say if you are only seeing one number, its most likely at the lowest magnification. Look for companies that post both, like Nikon. :)
 
New to hunting, empty freezer. just bought a tikka t3 30-06 now I'm shopping scopes. where do I spend my money? I want a solid set-up, $100 for rings? $1200 for a few more minutes of shooting is the low light hours? Any advice would be great.
 
Quick question regarding MOA. I have a AimPoint CompM2 that has a 4 MOA dot according to there specs, it also states in there specs that it is "1 MOA ˜ 30 mm at 100 meters ˜ ” at 100 yards".

My head isn't to clear this morning, how can the MOA dot be 1" at 100 yards when it states it is a 4 MOA red dot? I figured it would be a 4" dot at 100 yards, basically meaning your target will be covered if it is 4" or smaller at 100 yards :confused:
 
Hi#



I'm going to buy a leupold mark 4 lr/t 6.5-20*50 tmr MNP 60080

Please introduce me to a seller who supplies this rifle scope
 
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