I now mark my bbl's so that I'm sure to match them with the same frame. I always am sure to match the same forend to a specific bbl and note the tightness of the screw. I shoot IHMSA a lot and as a result I will move bbls often. I've noticed up to about a 1" shift (sometimes a bit more...but not always) in POI when changing bbls. One inch when shooting at big game in the field is no big deal, but it can mean a miss when shooting 1/2 scale rams at 200. Luckily the first 5 shots in IHMSA are to confirm Zero and that is all I need to get the bbl back on track and on target. It is rare when I don't have to make some sight adjustment.

Bill in OR