[First Freedom]

Since I want to work on this today.

My rifle that has been nothing but trouble it seems (so far anyway), now has the problem of shooting 5 inches high at 100 yards (6.5x55mm ammo), even with the scope elevation adjustment all the way down, some 150 clicks or more from "center". No telling how high it would be shooting if I had the scope adjustment near center - I didn't test that - I had bore-sighted it down close to the bottom to start with, and it was 6-8 inches high at 100 yards before I turned it down all the way.

So, I have 2 shims for the front of the mount - EACH shim is 12/1000th of an inch. But, since this is a turn-in mount, it's a bit of a pain turning it in and aligning it each time. So I want to get it right the first time if possible.

So, my question is, should I start with both shims, or just one of the shims, to correct me back to near center of the scope's adjustment, given the facts/parameters I have given you. Anyone have a rule of thumb on this? I'm leaning towards trying 2 shims first, then going to either 3 shims or back down to 1 if it's still way off.

Thanks.

[First Freedom]

OK, this may help. There's 274 total clicks in the adjustment. Therefore, I was 137 clicks from center, which translates to 34". Add this to the 5" I was already high, and this puts me 39" high at 100 yards when I'm at center of adjustment where I want to be. So, 1, 2, or 3 shims of 12/1000ths thickness under the front of base to correct 39" at 100 yards with 6.5x55, 120 gr @2650fps?? I know it's also going to depend on the length of the scope base and scope, because of the "lever effect". But just wondering if anyone had a rule of thumb here?

[Eric of Indiana]

Dan, I don't think you have enough shims to adjust 39" @ 100 yards. By my calculations on an 8" scope base, you'd need to raise the front .086"
Eric

( Edited because the first one was for a 5" adjustment. )

[First Freedom]

Thanks Eric, I don't really need to correct the whole 39" - that would be the ideal, to get me to the center of the scope adjustment, for maximum flexibility, but I think I'm going to go with the 2 shims and that should almost certainly correct the 5" and a good portion of the remainder - good enough for my purposes - if not, I'll go with 3 shims - but think I'll start with 2 - its' not the end of the world if I have the crank the scope's adjustment towards the end - it's just that I've heard it can throw off your sight picture somehow, the further you get from center, though I'm not really clear on exactly what is "thrown off", technically. ??? In any event, what is the formula you used, Eric? Thanks.

[Eric of Indiana]

Here's the formula I used:

Distance off in inches / 3600 inches ( 100 yds ) = adjustment amount ( shim height ) / scope base length.

A little algebra, and you get:
( Distance off/ 3600 ) * scope base length = adjustment amount

[swifter]

I'd start with the two shims. When you remove your scope, place it objective bell down on a mirror and look thru the ocular. You should see two crosshairs. Fiddle with the adjustments until they are superimposed, and your scope will be centered. Easier than counting clicks...

Tom