Air Rifle Scope Mounting Basics
Scope Mounting Basics
Your brand-new airgun just arrived, and you are eager to try it out. You also purchased a air rifle scope (make sure it's airgun rated if you plan to install on a springer) and the recommended mounts and rings that fit, and all you need to do now to enjoy your new acquisition is to install the scope on the gun. So go ahead…..install the scope and get shooting!
What do you mean you’ve never put a scope on a gun before? Really? Oh….okay. Well, it isn’t hard, so let’s just walk through it together.
Airguns come in many shapes and sizes, and different manufacturers use different mounting systems. As a general rule, you will most likely find 3/8" (11 mm) dovetail grooves machined into the top of the receiver on the majority of airguns. However, some manufacturers use a different system that installs a rail on top of the receiver. Be sure to check the width of the rail so you can order the proper-sized mounts. If you come from the firearm world, and are used to Weaver-style mounts, there are adaptors that convert from dovetail to Weaver, allowing you to use mounts you already possess.
Now consider the air rifle you have purchased. Is it a heavy-recoiling springer? If so, you will want to take advantage of the scope stop that hopefully came with the gun. Often, you will find scope stop holes already provided by the manufacturer on top of the receiver between the dovetails. If the scope mounts you purchased have a scope stop pin, the pin goes in the hole to prevent the entire mount and scope from creeping back on you when shooting. If there are no holes provided, then you can install a scope stop near the rear of the dovetail that will provide that function for you. A one-piece mount is often a good investment if you have a heavy-recoiling airgun, in that it provides a longer gripping surface than a two-piece mount. They aren’t quite as flexible as a two-piece mount, but they are very stable, and lessen the need for a scope stop. If your airgun is a lower-recoiling type, either a low-powered springer or a PCP/CO2-powered gun, a scope stop is rarely called for as the recoil isn’t enough to cause your scope to creep.
Taking the top of the rings off the scope mount, place the mount or mounts on the gun and fasten them to the gun. Don’t bear down on the fastening screws yet, as you may need to make some adjustments.
Place your scope in the rings, making adjustments for a good fit, and place the top half of the rings on the mount.
Fasten the top of the rings just enough to hold the air rifle scope in place, yet allowing you to still be able to turn and slide the scope forward and back. Now position the scope so that the eye-relief is to your liking, perhaps 2” to 4”. (Eye-relief is the distance from your eye to the rear of the scope, the part that you are looking through). Once the correct distance is obtained, rotate the scope in the rings so that the scope is level in the rings. The vertical reticle in the scope needs to divide the gun in half when you look through it. Now that you have the correct eye-relief adjusted, and your scope is mounted evenly in the rings, fasten the rings down on the scope by alternately tightening the screws. On a four-screw ring mount, I normally do two on the front (diagonally positioned from each other), then two in the back. I then fasten down the others, alternating from front to back. It’s sort of like changing a flat-tire….you tighten the lug nuts alternately, not the ones next to each other.
Be careful that you don’t bear down too hard on the ring screws….you can damage the tube of your scope, which certainly isn’t your intention. After the rings are tightened down, go back and tighten the entire mount to the gun.
There is an issue that affects your scope-mounting procedures. It is called barrel droop, seen mostly in break-barrel designs. Since the open sights on an air rifle are on the barrel, shooting with open iron sights will not affect your point of aim. However, when you place a scope on the gun, the scope is mounted on the receiver, not the barrel. To compensate for the barrel droop found in some airguns, you must sometimes shim the scope in the rear mount to more closely align the scope with the barrel. There are different materials you can use, from tape to strips of aluminum cut from a drink can. However, to avoid having to shim the scope, an adjustable mount can be purchased that will allow you to make adjustments to the mount itself in order to compensate for barrel droop. The RWS C-Mount is a terrific mount. It is fully adjustable for windage and elevation and makes sighting in a scoped air rifle a breeze. You might think that you can just sight your scope in with the adjustments on the scope itself but sometimes the barrel droop is too severe for this and the scope will not have enough adjustments to get you on target. RWS air rifles are know for this and, therefore, the RWS C Mount is recommended for them.
Another option is to buy pre-compensated mounts that have a built in droop allowance already machined into the mount itself. It isn’t an adjustable mount, but the mount was purposefully machined with a slightly higher rear scope ring to allow the scopes normal adjustment knobs to be able to adjust enough within their normal working range to get you on target.
The following link will give you another visible demonstration of how to mount a scope, closely following the steps I outlined above.
Once you’ve mounted your scope, grab a piece of paper or cardboard, some pellets, and let’s go sight in your scope-mounted air rifle. Place the target about 10 yards away. Since we are so close to our target, protective eye wear would be a good thing to have in the event of a ricochet. Take a few shots at the center of the paper, seeking to just get on the page. Using the scope's horizontal adjustment knob, get the point of impact horizontally centered on the target. Once you’ve accomplished this, work on the vertical adjustment to bring the point of impact to about 1” or so below the point of aim.
Now move the target out to 30 yards away and shoot a group of 4 or 5 shots. Don’t worry about flyers that differ from the group at this point, concentrate on the group itself. At 30 yards, you should be close to dead on for most airguns. This will vary from gun to gun depending on the power of each gun. Don’t forget that if you shoot a different pellet than the one you used to sight in with, you will have a different point of impact due to the weight of the pellet and the fit of the pellet in the barrel. So sight in your gun with the pellet you intend to use. Mounting a scope isn’t hard, and the method described above will suit the vast majority of airgunners. There are more advanced methods for FT shooters and accuracy devotees that involve using a level, working up a chart to plot the impact point of each type of pellet, and adjustments to the scope for each shot that occurs at a different range. I’ve never used that method myself, finding the above method of scope mounting more than adequate for hunting and plinking.So now you’re ready to go shooting. Enjoy!