B-Square M1 Scope Mount
July 24, 2014Civilian Marksmanship Program▸Armorers Corner▸B-Square M1 Scope Mount
INCLUDING WHAT YOU WILL NEED TO INSTALL IT, SIGHT IT IN AND MY EXPERIENCE SHOOTING WITH IT
By: John McLean
I started this evaluation with low expectations because of reports from others over the years that this mount would not allow the scope to hold a zero, when I finished the installation and testing, I was surprised at the relatively easy installation and how well it held a zero during my testing. The fact that this system allows a rifle scope to be mounted without any modifications to the rifle other than removing the rear sight makes it a good choice for anyone with a good M1, a scope and aging eyes.
The photo above shows my installation. The scope is a used Tasco that I bought for $20.00 and the 1” rings come with the mount system. The blue arrow shows the main attachment bolt that the whole mount pivots on, it comes with a black plastic knob molded to the end that broke off as I was tightening it. I recommend breaking the knob off and digging out the part of the plastic knob that fills the 3/16 allen wrench socket. I found that being able to use an allen wrench to assemble and disassemble it was an advantage. Be careful not to over tighten due to the unsupported rear sight ears.
Take note of three important things in this picture:
- The white arrow shows the two brass shims that I had to use to get the scope and mount moved to look more to the right as my initial shots were out the right side. I used some .015 brass shim stock I had to make them. Your rifle may require the same rough windage adjustment as my rifle did, or you may need shims at the front to compensate for shots going out the left side, or you may not need to use shims at all.
- The two red arrows show the set screws that will allow you to rough in your elevation setting. It is not necessary to get these screws much more than snug, you just want to remove all clearance beneath them where they contact the receiver. If you try and tighten them down all you will do is warp the mount due to the leverage situation with the front screw. I found that having the front screw protrude approximately 1/16”, and the rear screw 1/8” out of the bottom of the mount was a good starting place.
- The green arrow shows the “L” bracket and screw that holds the front end of the mount to the receiver. As you are getting your mount’s rough elevation and windage adjustment set, make sure this screw and bracket are snug but not tight. When you have finished with the rough sighting and all necessary shims are installed, you can tighten this one down appropriately with the rest of the screws. Don’t over tighten the screws.
Aside from the tools needed to make the shims and the screwdriver needed to remove the rear sight, this is all I needed to make the rifle ready to fire and make the final zeroing adjustments to the scope. The three allen wrenches are: 3/16, 1/8 and 5/64.
To make the shims all I needed was the shim material which is available at hardware or hobby stores. You can also make your shims from aluminum or steel drink and food cans. The shears and punch set are good to have but you can also drill the 1/4 “ holes and use heavy duty scissors if you need to.
- Before you begin the sight in procedure, make sure your scope is adjusted so the cross hairs are in the center of their movement for windage and elevation. To find the center, simply count the number of clicks your scope has from stop to stop for elevation and windage and divide by two.
- Because of the scope being higher than the original sights, you will probably find that you will want to purchase one of the reproduction cheek pads designed for the Garand. During the sight in process though, several rags laid on or wrapped around the stock where your cheek normally rests will help get your eye up to where it needs to be.
- Start the sight in process by shooting from a rest and at 25 yards or so to make sure you get on paper.
Aligning the mount:
Your first shots at 25 yards should tell you how far off the alignment is between the barrel and the mount.
Adjust for rough elevation using the two set screws.
Remember that if your shots are high, you raise the front of the mount. If they are low, you will lower the front of the mount.
Adjust for rough windage by adding shims as necessary.
If your shots are out the right side, add shims at the rear main attachment bolt to move the rear of the mount to the left to compensate.
When your shots are roughly centered on your target, move the target back to 50 or 100 yards and adjust again as necessary to get your shots on target. Once you are on paper at 100 yards, snug down the main attachment bolt and the screw that secures the “L” bracket. The set screws that adjust rough elevation for the mount are not to be tightened further, just make sure there is no clearance beneath them so the mount won’t rock back and forth. At this point you can use the elevation and windage adjustment on your scope to make the last fine adjustments to center your shots.
My experience shooting with it:
Once I completed the installation and made my final alignment adjustments, I fired a hundred rounds of Greek 30-06 ammo to see how it held up. My grouping started off centered and gradually rose slightly up and right to finish with my bullets generally impacting in the 8 and 9 ring at 2 o’clock. My guess is that it took a little while to settle into position. During my testing I did not find that any of the mount hardware loosened up but it is something to keep an eye on.