My mates 6x42 is about 4" low at 100yards screwed as high as it will go.

Mid point to highest is 60 clicks which is 60cm. Presumably his mounts need adjusting to be on roughly in the centre ie to be 60cm higher.

By how much does the front have to be lowered, the rear heightened or both?

What action is on your friend's rifle, and what rings and bases is he using?
My point here is, it sounds like you friend may be using an incorrect ring/base system for the rifle action.
With good actions, it is relatively easy to find the right combination of rings and bases that will have him shoot without the problem he faces now.

Incidentally, shimming bases is the low road.

Don

I just had a fellow in the shop the other day with the same problem. Only thing was, he was moving the adjustments the wrong way. In other words, if his bulet was shooting low and he wanted to move it up, he looked at the adjusment and moved it down until he ran out of adjustment. He was moving the scope in the direction the bullet was, not moving the impact point in the correct direction. This is the second time I've seen this. Make sure your mate is not doing this.

To correct his problem, I would try to optically center the scope and then by trial and error, add .010" shims until the scope is centered in the collimator.

On at least one of my rifles, I did all I could think of to correct for this kind of problem and in the end, I had to ream the rings, they were so far off. Lapping may work also, I just happen to have a 1" reamer made by Clymer so I used that. By the way, Clymer makes this in 1" and 30 M/M, not cheap by any means. It is long enough to fit between any reasonable length receiver mounts.

quote:

Originally posted by 1894mk2:
My mates 6x42 is about 4" low at 100yards screwed as high as it will go.

Mid point to highest is 60 clicks which is 60cm. Presumably his mounts need adjusting to be on roughly in the centre ie to be 60cm higher.

By how much does the front have to be lowered, the rear heightened or both?

If front and rear rings are 10 cms apart, a 1mm change on the height of one of the rings will result in a 100 cms change at 100 meters.
It’s just simple mathematics.

B.Martins

quote:

Originally posted by Jim Kobe:
I just had a fellow in the shop the other day with the same problem. Only thing was, he was moving the adjustments the wrong way. In other words, if his bulet was shooting low and he wanted to move it up, he looked at the adjusment and moved it down until he ran out of adjustment. He was moving the scope in the direction the bullet was, not moving the impact point in the correct direction. This is the second time I've seen this. Make sure your mate is not doing this.

Ha Ha, last week I put a red dot sight on a sons 22 and it took me about 15 shots to realize the adjustments moved the dot and not the point of impact!

I'd try the Burris Signature rings, with adjustment inserts.

flaco

Rear base given one shim - now on target with 30 clicks left. My thanks to BMartins for answering the question asked!