Ok I know I have seen it in the past with some of the browning guns. They say 742 bore but have seen some come in down to 737. Now with the new A5 had two in the shop and one was 739 other one was 745. So for all of you that have guns that don't put up the numbers that the others put up this may be why. Folks point fingers at chokes or shells. This is why some will want a 660 some may want 650.
Thanks William for that insight....you'd think the tolerances would be a little closer than that.