One area of rifles that is often overlooked when building a precision rifle is proper fitting of sights and scope mounts. Even custom actions and good quality scope mounts almost never fit perfectly together, and many production actions and mounts fit so poorly together that the scope tube is actually bent when the screws are tightened down! Damage to the scope tube surface is also highly likely.
Rifle scopes are precision optical instruments and don't take too kindly to being bent or distorted out of alignment..
Shimming and lapping the rings is often the solution and i recommend this service to anyone who owns a scoped rifle.. Shimming the bases and then lapping the rings in position ensures that the rings are in perfect alignment and that there is no stress placed on the scope tube. This not only maintains the designed optical and mechanical precision of the scope itsself, but also results in much greater clamping surface area which helps to stop the scope moving in the rings under recoil impulse and greatly reduces the likelihood of damage to the tube surface finish.
It is also a vital part of "stress free bedding" as the receiver and scope are effectively matched together in a very precise way, imparting no stresses on either the scope tube or the receiver.
I also manufacture my own brand of precision scope rings, for more information check out the Products page.