Questions on my PU scope mount base.

A few years ago I was able to get one of the Samco PU sniper rifles at a local shop. I purchased one of those reproduction mounts at a gun show. Unfortunately the holes were about 2mm too close together and it was one of those aluminum bases. I was able to get it fitted, but wasn't happy with it at all. Then I found out about the Accumount scope mounts I measured the distance and sent for the scope mount that best fit my needs. It mounted fine, but I find that I have to shim the front of the mount about 1/10" away from the receiver in order to get it aligned with the bore. Has anyone else had to do anything like this? The shimming started when I ran out of room to file down the rear of the mount.

The mount is secure and the rifle will shoot dime size holes at 50 yards with Privi Partizan 150 grain soft point ammo. Probably much better in the hands of a better shooter. I just wanted to know if anyone else has had to go this extra distance to align their mount.