Choosing a correct rifle scope is not less important than choice of the rifle itself. If you want to choose a worthy scope for accurate reliable rifle then it should cost at least half the price of your weapon. A scope with such price ratio will uncover the potential of your rifle in the best way. Of course it can cost much more but it should never cost less.
It is hard to find two similar scopes but finding two identical scopes is harder. Despite the fact that the exterior can be completely or almost identical, they may still differ from each other. In addition, the price on the rifle scopes with same characteristics and similar appearance may vary 10-20 times! So what is the difference?
Lenses are the main parts!
The Rifle Scope is a complex optical instrument. Its design is as complex as the design of camera lens or a telescope. And what is most important in an optic? Right… it is the quality of the lens!
Lenses are the most important things in the scope. This is what forms the image. So how do you make a choice and understand the difference between?
First of all, the image quality depends on the chemical composition of the glass and its method of manufacturing. While Cheap Chinese rifle scopes have poor quality glass, you won’t find this problem in the pricy US models. The smallest defects in the glass are invisible to the naked eye – the bubbles, smoke, or pebbles -not only make the image blurry, but also distort it. Insufficiently clear glass will significantly reduce aperture ratio of rifle scope that will affect your shooting in low light conditions or at a high magnification.
All these drawbacks and defects often occur in cheap scopes. So if the budget allows you to buy a quality product then you should do it. To make a really good rifle scope manufacturers use special optical glass. This glass has outstanding characteristics (transparency, uniformity, dispersion and refractive power) and can be used in camera lenses, telescopes, binoculars and other optical apertures.
A good lens should also has perfect shape and an ideally smooth surface. It passes many steps of mechanical manipulations before taking its place in the optical system of the rifle scope. Clarity, color, detail and, most importantly – the health of your eyes depends on quality manufacturing of lenses. This process is very consuming and complex. Observation of a target using dark and muddy scope is very unpleasant and an unwelcome burden to your health. So it is better to use clear and light optics.
Lenses are coated with special multiple coating which reduces the reflection of light, making the image brighter and producing contrast. Well-known manufacturers keep the secret of this coating so manufacturers of cheap scopes don’t reproduce their product and maintain poor quality of coating.
Such manufacturers as Leupold, Nikon, Redfield, Burris, Zeiss, Bushnell, Trijicon are recognized masters in the production of rifle scopes.
Objective Lens Diameter.
Characteristics of the scope and its use will highly depend on size of the objective lens. Large objective lens has its obvious benefits, such as: better light transmission and larger exit pupil at high magnification (see below).
But on the other hand – such a rifle scope would be big, heavy (which is highly uncomfortably if you have to walk with your weapon a lot, especially in a deep woods) and required higher mounting, which makes it less comfortable to shoot. Sometimes they are too “delicate”. Rifle scopes with large objective lens traditionally are not mounted on spring rifles because of the two-way recoil generated by the mainspring, which can cause damage to your scope.
Size of objective and ocular lenses determine such important characteristic as exit pupil — the small circle of light that appears in the eye-piece when you hold a scope at arm’s length. There is an easy formula to calculate exit pupil: you need to divide the size of the objective lens in millimeters by magnification. Exit pupil size is larger in scopes with large objective lens and small magnification. Ideally, this value should match the size of the shooter’s eye pupil. However, the human eye flexibly adapts to light changing. In the dark pupil can extend to 6-7 mm, and in the bright light narrowed to 1 mm. By age 50, the maximum eye pupil may be close to 5mm. The rifle scope does not change its characteristics yet for shooting at dusk it is necessary to reduce magnification or use a scope with better aperture and light transmission.
Thus, the larger the exit pupil – the easier it will be to use such a scope. To an untrained shooter, a scope with an exit pupil of more than 7 mm is perfect, while its value of 1.5 mm may create difficulties even for experienced shooter.
Field of View (FOV).
This is an amount of view you see through your scope from right to left at that distance. It is measured in degrees or feet at 100 yards. Wide field of view allows you to monitor and search your target with more convenience. Note that larger objective lens size does not extend to the field of view. That depends completely on the construction of the scope.
What do you need to know about magnification?
Magnification is one of the most important characteristics of the rifle scopes. It determines where you can use your scope and where you cannot use it. The 3x-9x magnification is standard for the white tail deer. While for antelope or mule deer in Western states it is better to use 4x-12x or 4.5x-14x because of the longer average shot than it would be in eastern whitetail woods. A 6x-20x or 8x-25x scopes does not have too much power for prairie dogs or long range target shooting.
Before we go into further details it is worth to mention that magnification of 4x does not mean that image will be 4 time larger then you can see with the naked eye. To understand right way what magnification is – we need an example. Let’s say you’re looking at a target from the distance of 100 yards. And if you will take a look at it through rifle scope with magnification of 4x, the image will become the same as if you would look at it from the distance of 25 yards. So the target actually became 4 times closer to you. Thus it will become larger, but not 4 time larger. The real increase of the size will depend on distance to your target.
Magnification of the rifle scope can be fixed or variable value. If it is variable then you can adjust it with the power ring on the eye bell. On the one hand variable scope is more universal. On the other hand not everybody needs it. There are many people who buy variable scope, put it on some particular magnification and never change it. In addition, the image in such scopes sometimes is not really good. It becomes unclear, dark and non-contrast. So if you want buy a scope with 4-16x magnification and going to use it exactly at 16x, then it is better to choose something else. For example, 6-24x will give you acceptable picture for sure at 16x or even at 20x.
Everything is different with the fixed rifle scopes. First of all their optical systems contains less lenses which reduces the loss of the light inside of the scope and has positive impact on the image quality. Secondly, their internal mechanics are simple, which makes them more reliable. So if variability doesn’t make any difference for you it makes sense to choose a fixed scope.
Rifle scope body.
Expensive scope’s body usually is made as a single piece from duralumin. It is sealed and filled with nitrogen. Nitrogen protects lenses from sweating when temperature changes suddenly. Therefore, you must never disassemble your scope.
The narrowest and longest part of the scope is called the tube. Image turning system (turns the inverted image created by the objective lens into the direct) located inside of it which is connected with elevation adjustment. Mounting rings that holds scope on your rifle goes on tube as well.
There are two different tube sizes: 1 inch (25.4mm) and 30 mm in diameter. There is an opinion that the 30mm tube transmits more light. But it is not true. Increased diameter allows the scope to have a greater range of elevation and windage adjustment. Scopes with the tube of 1 inch have been successfully sold and used as well as the 30mm scopes. Recently, scopes with tube diameter of 35mm became available as well!
Focus and parallax.
Another important parameter is the scope focusing system; it is also a system of parallax adjustments. What is it and why do we need it?
Just like any other optical instrument the rifle scope has its own focus distance. In other words, this is the distance to the target that allows you to receive a perfectly clear picture. So the focusing system helps us to adjust the scope for distance that we need.
In rifle scopes there is also such an unpleasant phenomenon as a parallax. Parallax is a shift of the target image in relation to the reticle if the eye moved aside from the eyepiece. This occurs when the target image is not focused in the same focal plane as the reticle. The rifle scope becomes sensitive to the position of your head relatively to the eyepiece if the target is not in the focus of rifle scope. This will definitely affect your shooting. That’s why it is important to focus your scope correctly before shooting.
Parallax adjustment (focus) may also serve as a rough range finder over short distances, if you use range scale, especially for the high magnification rifle scopes. For the target shooting called “field target” owners of such scopes use large parallax adjustment wheel. This allows them to estimate distance to the target with an accuracy of up to 1 yard.
For the air rifle, it is also very important to know the minimal focusing distance of the scope. The fact that the rifle scopes are designed for firearms (and those in the range of well-known brands is much more than “air scopes”), are not suitable for shooting at distances of less than 40-50 yards. Objects that are closer will appear in the eyepiece blurred and indistinct. So you cannot actually use such scopes with air rifles because the usual shooting distance for them is 10-50 yards.
For air rifle you need a scope with an adjustable objective (AO) so you can focus it to very close distance such as 10 yards. If you use a spring air rifle, you need the anchored optics as well. Such optics is anchored front and back to handle the forward and backward recoil caused by the mainspring’s movement. It will prevent your scope from destruction.
There are also rifle scopes without parallax adjustment. They are focused usually on distance of 100 or 150 yards where the parallax is practically reduced to nothing. For such scopes you will find “parallax free from 100 yards” in description. Such scopes use for long range shooting. For shooting from closer distance they would be extremely inaccurate.
By this we mean all the mechanisms provided for adjustment whether it’s the focus, magnification, or elevation adjustments. So what is worth paying attention to when you choose a rifle scope?
First of all, you should look at parallax adjustment (focus) system. It can be at the objective (adjustable objective), on the side of rifle scope (side focus) or at eye (ocular) bell. There are also models without parallax adjustment. More comfortable and precise is the side focus system. It allows you to make adjustments while you are looking trough the scope and if you have large adjustment wheel it can be done even more accurately.
Secondly, you should take a look at turret elevation and windage adjustments. The simplest rifle scopes allow infrequent adjustments (when you sighting in your scope) using screwdriver or a coin. At the same time, tactical scopes with large turrets allow you to make adjustments at the field, which is convenient to do even when wearing gloves.
Adjustments made in minutes of angle (MOA). So it is 1 minute (1 degree) or 1.047 at 100 yards. In practice, it is called 1 inch at the 100 yards. In most cases, rifle scope adjustments are made in ¼ MOA or ¼ inch increments at the 100 yards. So each click moves the point of impact a ¼ inch at 100 yards. The same click moves the point of impact ½ inch at 200 yards, 1 inch at 300 yards and so on. Some scopes move the point of impact ½ inch, some of them have no clicks at all.
If you are sure that you will need to make adjustments “at field”, then tactical turrets are what you need. If shooting will be conducted in the same range then the type of turrets is not as relevant. In such a case, large tactical turrets will only hinder.
When you are testing a scope that you just bought in first place check it’s repeatability. Using the cheaper models of rifle scopes frequently you can see the situation where the point of impact doesn’t go back to zero (e.g. let’s say you adjusted the target point 3-4 inches up and then return to the initial position – it should match whatever you had, but it doesn’t happen). Such mechanics may not indicate that the scope is bad, but it will not allow you to make adjustments in the “field”.
There is one more thing to mention. If you are going to shoot from air rifle at the long distance (around 100 yards) you will need a scope with good margin of elevation adjustments – no less than 30 MOA or even more. Otherwise at the distance of 100 yards you will not be able to see the point of impact.
You should also remember about eye-piece (diopter) adjustment which allows you to adjust optical system of the rifle scope to your vision. The correct setting will reduce eye fatigue and improve visibility of the reticle. Usually this adjustment is located on the eye bell of the scope closer to shooter. Once you adjust the reticle for optimum sharpness (look at the sky or other neutral background), you will not need to do it again.
Reticle is simply a cross-hair or an aiming point in your field of view. It helps you target, determine distance to the target, and more. Today there is a great variety of reticles. We cannot even list all of them. They are all modern prototypes of the classical reticles, such as Crosshair, Duplex, German Reticle, Target Dot, Mil Dot, Circle, Ballistic and SVD Type.
Each of them has its own purpose. Last few years the most popular used to be the Mil Dot and its modifications. This reticle is used by military snipers and allows a quick estimate the distance to the target. The dots also can be used for hold over if you know.
Mil Dot has dots in increments of one mil. Mil means mil-radian, not military. Mil-radian is 1/1000 of radian or 1/6283 of a circle. A mil in a reticle subtends 3.6″ at 100 yards. To find the approximate distance to your target, set the required magnification suggested by the manufacturer. Then you should know the approximate size of your target. If your target is covered by 1.5 dots, the size of it is 1.5 mils. Then you need multiply the size of your target in yards by 1000, and divide by size of your target in mils. If your target is 1.5′ tall, you need a 0.5 yard setting. So 0.5 x 1000 = 500 and then 500/1.5 is approximately 333 yards. So as you can see calculations may take a while. Mil Dots are rarely used anymore and if you want to determine distance to the target it is easier to use a laser rangefinder.
Focal plane of the reticle.
This future is only matters for variable rifle scopes. Reticle may be located in the second focal plane and do not appear larger as the magnification is increased. Or it may be located at the first focal plane. In the variable scopes with FFP (firs focal plane) reticle image appears larger while you change magnification.
Almost all rifle scopes in US market have reticle in second focal plane.
How do you read the numbers?
Almost all scopes that you will find in US market will have their name looking like this: Leupold VX-2 6-18×40 AO. Everything is very simple: Leupold is brand, VX-2 is model, 6-18x is magnification, 40 is size of objective lens in mm. And the letter that comes after is not always easy to understand, so let’s see what they mean:
AO – Adjustable Objective means that you can adjust focus of the rifle by turning of Objective ring.
SF – Side Focus means that such scope has side parallax adjustment (focus).
RF – Rear Focus, ability to adjust focus on eye (ocular) bell, just on the fixed scopes.
IR – Intensified Reticle means that it is illuminated.
AR – Air Rifle, such scope can be mounted on spring air rifle.
MD – Mil Dot
FFP – First Focal Plane (see above).
FT – Field Target, rifle scope optimized for such type of shooting
BDC – Bullet Drop Compensation