I bought a Mosin at a gunshow with a beautiful bore for $75. Didn't notice the front sight had been driven all the way to the left. When I shot it the group of 5-6" was way left.
Took it out of the stock and found the stock severly warped. Corrected the problem with my handy Dremell and had to move the sights back to center.
Also got some 2" groups.
To correct the high impact I pushed a small piece of tubing down on the front sight. Trim to length as needed.
The tubing came from a small wire removed with a wire stripper.