Graybeard, I'll throw out an idea, based my on almost 30 years of production machining experience (although not gunmaking), and your similar length of time mounting scopes. (Meaning you know what you are doing!) The holes are not in line with the bore. It is probably not a coincidence that the guns shoot to the right. Factory fixturing is based on the fact that 90% of the folks using it are right handed, so errors in mounting parts, tightening work holding fixtures, or even blowing out chips before the next piece is loaded, usually result in defects occurring on the same side of the workpiece, or in the same direction, time after time. Quality control (inspection) goes out the window fast when production schedules are not being met, so these things get through more and more, lately.