There is a very wide variety of scopes mounts for airguns, differing in height, style, adjustibility and so on, but all generally fall into one of two categories: One-piece mounts, and two-piece mounts. Each has advantages and disadvantages.
One piece mounts generally offer a wider range of adjustibility than do two piece mounts. In the pictured B-Square mount, it’s possible to adjust the verticle tilt of the scope over a very wide range- useful in some break barrel guns and in scopes with limited reticle adjustment range. These mounts are often better at resisting movement due to recoil, owing to the very large contact area between scope and dovetail. Many also feature built-in recoil stop pins designed to engage a recess machined into the top of a spring air gun.
But not every gun and scope combination has room for a one-piece mount. Loading ports, cocking levers and other mechanisms can intrude, and that’s where seperate mounting rings come in. Some airgunners also like the simpler, cleaner look of seperate rings, particularly on finely finished custom guns. It’s possible to buy very finely finished, polished moutning rings designed for high-end .22 rifles that will also fit a standard airgun dovetail Whichever you choose, the same general considerations involved in mounting a scope are applicable to both.
Before you do anything else, line the mounting rings with a single layer of electrical tape. This will provide cushioning, protect the tube from scratching, and help the rings grip the tube without excessive clamping force. (Some mounts come with a layer of cloth tape inside; I think the vinyl electrical tape does a better job.) Attach the rings to the scope loosely at first, so that you can find the best mounting position and identify and problems of fit.
Attach the rings to the gun- again, loosely. If you you may find at this time that the bell of the scope- the end facing the target- interferes with the barrel, particularly if it’s a very large scope. If so, you’ll have to get taller rings or a taller mount. Raise the gun to your shoulder and look through the scope. Adjust the rings and the scope fore and aft so that you can get a good scope picture- that is, you can see a full image- with your head and neck in a relaxed position.
Once you’ve found a good position for the scope, add a drop of Loctite (blue formula) to the dovetail grooves and tighten the screws that attach the rings to the dovetail. This will help tremendously in keeping the scope and mount from moving; in many instances, I’ve found that recoil stops are unecessary using the Loctite technique.
Now it’s time to level the scope. Locate a target with a long horizonal line far enough away that your scope can focus on it. This can be an actual target, a line drawn on a basement wall with the aid of a bubble level- whatever you can find in the way of an accurate reference. Next, level the gun. If you have a gun vise, that’s great, but this can also be done with a rest and a sandbag or beanbag. Place a small bubble level on a flat part of the gun, and level it. Many break barrel guns have a flat area machined at the rear of the barrel; this is a good reference point. If you can’t find a good reference point, do the best you can, and we’ll refine level when we sight in the gun.
Rotate the scope in the rings so that the target is level with the crosshair. Carefully tighten the clamping screws- going back and forth between the two rings, and alternating left and right, and constantly checking level.
Your scope is now mounted and leveled, but there’s one more task- sighting in. That’s in my next post.