BSA adjustable scope mount
by B.B. Pelletier
The BSA adjustable scope mount is a recent development. It promises to solve one of the difficulties encountered with B-Square adjustables, namely that if the elevation has to be adjusted, the scope must be removed from the rings. The design of the BSA mount allows you to leave the scope in the rings, but it introduces another problem that the B-Square mount doesn’t have. I’ll cover that when I come to it. Let’s take a good close look at this new mount.
Currently this new one-piece mount is issued with one-inch rings, only. So if you have a scope with a 30mm tube you must use something else. And this is a one-piece mount, so you give up some positioning flexibility to use it. But its largest shortcoming is the lack of any kind of built-in scope stop. If you want to use this one on a spring pistol rifle, you must install a secondary scope stop. The combination of that and the limits of a one-piece mount may push the eyepiece too far from your eye. However, because both rings are on the same plate, no amount of elevation adjustment can put any strain on the scope tube.
How does it work?
The mount has an elevation wheel in the rear and a windage knob up front. Of course nothing prevents you from mounting it backwards so those positions are reversed, but since the majority of barrel problems are drooping barrel angles you’ll probably want the elevation at the rear. Refer to the post on barrel droop for a better understanding of the problem.
To elevate the rear of the scope, loosen the locking screw and turn the elevation wheel. The upper plate of the mount to which both rings are attached has a spring under it, so it travels as high as the adjustment wheel permits. Locking this wheel freezes all elevation adjustment solid. However, this is where this scope primary flaw is revealed.
The elevation wheel is located at the rear of the mount. The locking screw at the lower rear must be loosened before adjustments can be made. The sharp downward angle shown here is just to illustrate the function. Notice the spring under the scope ring.
Because it has no scope stop of its own and must be butted against a separate stop, the locking screw for the elevation wheel is hidden when the scope mount is butted against the scope stop. So each time you want to elevate or lower the mount, the clamping screws that hold the mount to the dovetails have to be loosened and the scope and mount slid forward to gain access to the locking screw. In practice it’s only a little faster to install than the B-Square mount, plus moving the mount every time means that it needs to be returned to the same place on the rifle each time, or zeroing will take longer. On rifles with short dovetails there is no room to slide it and the procedure amounts to removing the scope and mount from the rifle every time the elevation wheel has to be adjusted. This could easily have been avoided if they had positioned the locking screw on either side instead of at the rear.
Windage adjusts at the front of the mount, via a knob that looks like it came from a scope. It has click detents and the amount of adjustment (1/4″ per click) inscribed on the outer plate. It has to be unlocked before it will adjust, just like the elevation wheel, only being located at the front means the locking screw is always exposed. This is a great design! It’s much easier to use than the B-Square push-pull windage adjustment screws, and it’s the only one on the market with definite adjustments and click detents.
Windage knob at the front of the mount has click detents, each moving the strike of the round 1/4″ at 100 yards.
Windage dialed all the way to the right (looking back on the mount). It will go just as far in the other direction. The locking screw at the bottom is easily accessible at the front.
Of course when adjusting the front of a scope you want to move the scope in the opposite direction that you want the strike of the pellet to move. It’s the same as adjusting the front sight on an open-sighted gun.
Will it work for you?
The BSA has quite a few limitations that need to be considered before ordering. For starters, it will not work with RWS Diana rifles due to the lack of a vertical scope stop screw. And since it is one-piece, it doesn’t give much scope positioning flexibility. On the other hand, some rifles seem to be made for it – like the Mendozas that have a built-in scope stop the mount can butt up against.
Time will tell if this is a good mount. If any readers have experience with it, please tell us how you like it.