Another observation - I had a mauser that had been D&T'd, with hole spacings for 45/46 bases. Ran out of vertical adjustment in the scope trying to get sighted in. Substituted a 55 rear. Ran out of adjustment the other way. Had to put a shim under the 45 to get it to sight in. Point taken was that no guarantee that whomever ground the stripper clip lips actually left the original rear bridge surface intact, and therefore, I believe Weaver's and other scope base manufacturer's dimensions are based on an "average" which may or may not exactly apply to your rifle / rings / scope. That episode also got me into a lapping bar and learning to use it, at least as a check, for every set of rings I have mounted, since.