BAM B40 in .22 caliber: Part 3

Part 1
Part 2

by B.B. Pelletier

Let’s move right along. Now that the rear ring is secured against the scope stop, it’s time to attach the front ring. Get it attached to the dovetail but don’t tighten it yet. First, you have to determine where it should go. Use the scope for this. The scope has a tubular area on each side of the turret where the scope rings will clamp. I like to position each of my rings close to the middle of this area. This is where two-piece rings are better than one-piece, because with one-piece you have no choice where the rings are. Positioning either one of them also positions the other.


The rings are installed, but the front ring still needs to be positioned using the scope.

On smaller scopes, this tubular area is short. The scope I’m using is considered a compact scope, but Leapers also makes some compact scopes that are even smaller. The smallest of these absolutely must have two-piece rings, as there is no room to maneuver. The reader who asked for this post was obviously concerned about a scope being too long for the B40, so the objective bell would be located over the place where the rifle is loaded. There is no fear of that! I positioned this compact scope too far forward because of the recoil stop that was used. If the rings had had a stop pin, I would have mounted the scope another inch back. I could still slide it back a little, as the picture shows, but I left it there for the sake of clarity. Lift the rifle to your firing position and check the eye relief of the scope. If you do this carefully, the scope will stay put.


Position the front ring with the scope, so there is equal distance on either side of the ring. Then tighten the ring in place.

Once you slide the front ring to where you want it, tighten it and the rings are mounted! The next step is to attach the scope caps and position the scope.

Attaching the scope caps
I’m using 4-screw scope caps and so should you. The 2-screw caps are too narrow and put too much force on the scope tube when tightened. You may not notice this on a Leapers scope because its tube is machined from a solid billet of aluminum; but on other scopes that have thin tubes of drawn aluminum, denting will occur. Do not tighten the caps yet.

Leveling the reticle to align the scope
This is an easy step, but shooters go to great lengths to make it complex! Simply align the scope until the vertical reticle seems to bisect the rifle. The drawing should help. Believe me, I have used collimators, I’ve leveled the gun and scope against a bubble level at 50 yards and I’ve gone through all sorts of silly gyrations. Nothing works better than what I’m showing you here. You don’t need any tool for this; you do it by eye. And, every time you pick up that rifle, the scope alignment will look right to you because you aligned it yourself!


Simply move the scope until the vertical reticle bisects the rifle.

Tighten the scope caps
This next part is important. Don’t randomly tighten the cap screws. There’s a procedure. Look at the picture. Starting with the front cap, tighten the top right screw. Tighten it only until it is snug – no more. Then, do the same to the lower left screw. You have now snugged two of the four screws on that cap. Move to the rear cap and do the same – top right and lower left screw. Come back to the front cap and tighten the top left screw, followed by the lower right screw. Do the same for the rear cap screws.

Go around again in the same pattern as before. Keep doing this until the screws no longer move. This procedure will be recognized by mechanics as the same one used to torque the cap bolts on connecting rods in an engine. It spreads the force as evenly as possible. The cap screws do not have to be incredibly tight to hold well. They just have to be uniformly tight.


Use the pattern of tightening recommended in the text.

That’s it! Once the rings are tightened, you’re ready to sight in. If you later discover that the scope seems to be canted, you can always go back and do the alignment procedure again. After you’ve mounted a few scopes, the process becomes second nature and goes pretty fast. This would be a good time to read Tom Gaylord’s article about how to sight in a scope.

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