Sometimes when you mount a scope – something just aint right and you can’t get the scope aligned properly to get it bore-sighted. Slight errors in the making of the base or rings or something… Many reasons… but the result is that to get the scope bore-sighted right, you have to shim the scope. Don’t panic. And don’t go off and order some expensive Shim Kit. And don’t use Paper shim. They compress and get thinner over time. You don’t need to spend any money… well, maybe 75 Cents at most. You can make your own Shims. It’s easy to do, and I do it all the time. I am a professional, and I’m telling you – you can do this at home. It’s Ballistic Science, but it’s not Rocket Science. All you have to do is to make some Beer Can Shims.
Now, they are called Beer Can Shims, because that’s what they were called when I learned of them… at Ft. Benning. They called them that, because that was what they used. They specified the use of Bud Light cans, but you can use Miller, regular Bud, Guinness, or any variety… for Mormons, you can use Mt. Dew, Coke, Pepsi, Full Throttle, Monster… because really, the brand is not important – but a Benning the SOP was Bud Light. Just sayin. Personally, I prefer Rockstar.
You use some shears, open the can up, and cut off the tops and bottoms. Trim up sheet and section it, then cut it into strips. The width and length are up to you. 1 inch tubes will use shorter ones than 30mm tubes.
When you put them in the ring, under the scope, check the bore-site to make sure that you get the right amount. Don’t use more than 4 shims. If you need more than 4, you need to rings and bases or there is something wrong with the gun. Typically I use no more than 3. When stacking them, but down a long one, then a shorter one on top, then a shorter one than the last. You don’t want to shim the sides, just the bottom. If you are shooting too low, shim the Rear. Too high, shim the front. Simple stuff… unless you get it wrong.