Bart Bobbitt wrote a bunch of accuracy papers in tandem with McMillan. He wrote a pretty good paper on this topic. They found that most manufactured rings when mounted have different centers to the axis of a straight scope and therefore most will bend the scope tube to varying degrees. IIRC, they determined this bending of the scope tube generally caused an error of around 1/4-MOA that would bind the internal mechanics so that the scope would no longer maintain tracking and would no longer be repeatable for accuracy . In some cases, the scope tubes bent even farther. The paper went on to say that correct lapping would center the rings on the scope axis which prevented any bending of the tube.
Flip side, I believe he offered an opinion along the lines that the "AVERAGE" user with a bent scope wouldn�t have the ability to notice loss of tracking, a loss of repeatability, or a loss of accuracy. I kinda agree with that, but it can go both ways. Some appear quite happy to slap pieces together straight out of the box to go kill game animals by the truck load with fairly inaccurate rifles. Others appear quite happy to build anal benchrest precision rifles to go kill the same truck load of game animals with crazy accuracy. Between those two ends, I�m sure there is plenty of room for the rest of us.
Best:)
