There’s a lot more to an Airgun Scope than meets the eye. More and more airguns come bundled with them, some are decent while others make good paperweights. How do you know what to look for when making an airgun purchase that includes a bundled optic? Or, how do you know how to pick the right optical upgrade for your favorite airgun? In these articles we’ll look to dissect the typical airgun scope to help you pick the good ones from the paperweights.
As we start this 2 part series, let’s look at why airgun scopes are different from other scopes. Airgun scopes are a special breed of scope as they must be designed to handle the reverse recoil of modern spring and gas ram driven airguns. All guns recoil backwards, what sets these specific airguns apart is the harsh jolt forward as the piston hits the front of the compression chamber. If a scope is not rated for this type of recoil, it will be a mess of parts in no time. I’ve heard horror stories of folks putting their $1000 Nikon scope on their spring gun only to have it reduced to a pile of parts in under 50 shots.
All scopes have some basic components. The quality of these components will determine the overall effectiveness of the optic. Starting from the rear most part of the scope you’ll find the eyepiece. This piece of glass is often adjustable for use with or without eyeglasses, providing a clear image to the user. This is sometime incorrectly called and confused for parallax focus. Having an adjustable eyepiece has nothing to do with an adjustable parallax, we’ll get to that later. It does allow you to adjust the image clarity to be suitable for your needs.
As you move forward, you’ll have the outer “tube” of the scope. This is generally an aluminum tube that’s filled to a positive pressure with nitrogen to prevent fogging and to help keep the scope waterproof. There are two common tube sizes. The most common is a 1″ diameter, however, more expensive scopes will have a slightly larger 30mm diameter tube. The larger tube allows more light transfer which helps in low light situations and higher magnification scopes (we’ll get to that later). Some of the really inexpensive bundled scopes use a plastic tube. This is one of the first signs that you may have a paperweight on your hand. Some of the low end Gamo rifles such as the Gamo Silent Cat use a plastic 4×32 scope. It will get you started, but that’s about all you should expect from it. Inside the outer tube is the inner tube which can house the reticle and other components, depending on the type of scope you have. The inner tube is what’s moved by the adjustment turrets to align, or “sight” the scope to your airgun.
As you look in the eyepiece and down the inner tube you’ll find the “reticle” of the scope. The term “reticle” refers to the crosshairs of the scope. There’s quite the variety of reticles on the market today. The first thing to note is if the reticle is a “wire” reticle or an “etched glass” reticle. Wire is the most popular type as it is the lesser expensive option. There’s nothing wrong with a wire reticle, but the etched glass is better and usually found on higher end optics. Etched glass reticles are more resilient to harsh recoil and will generally hold up longer than wire reticles. Some scopes come with a straight wire reticle. Others may have what’s called a “duplex” reticle, which has thinner lines in the center, changing to thicker lines further towards the outside of the field of view. The preferred reticle, whether wire or etched glass, is a mil-dot or some sort of range estimating reticle. Some scopes come with matching computer software that corresponds to the reticle, allowing you to calculate pellet drop. Hawke’s ChairGunPro is a good example of a software package specifically designed for their optics.
The next set of components you’ll find will be the adjustment turrets. All scopes have a horizontal and vertical adjustment. This allows you to “point” the optics in the right direction. These work by applying or releasing pressure on the inner tube that’s held in place via springs that oppose the adjustment turrets. This is important to note as you need to keep some amount of tension on the springs so that the scope maintains your settings. A good rule of thumb is that you should always have at least 1 full turn of adjustment left on your turrets. If you don’t have at least 1 full turn, then your point of impact may move around due to recoil. This is a common problem with some airguns when shooting at close range. The height of the scope over the receiver requires that you use a lot of “up” correction on the vertical turret adjustment. Be cautious that you don’t over adjust trying to move the point of impact up to the 10 ring.
As we continue to move forward, we find the front of the scope which is called the objective. You’ll see the objective size referenced in the scope description. A 4×32 scope = 4 power magnification with a 32mm objective lens. You may see a reference such as 4-16×50, which = 4 to 16 power magnification range with a 50mm objective. Generally a larger objective is better, providing a larger opening to gather the most light.
All that Glass
There are many lenses that comprise the typical airgun scope. All scopes should utilize coated lenses. This feature allows better light transfer and a clearer sight picture. The higher end scopes will have better coatings that can really make a difference when using your optic in low light or at the extremes of its magnification range.
This wraps up part one of The Anatomy of an Airgun Scope. In part two we’ll look at advanced features such as variable magnification, adjustable parallax, and reticle illumination. While these advanced features are not necessary, they all offer advantages that can be very useful to you as an airgunner, and they can help set apart the good optics from the paperweights.