I have drilled a LOT of small, deep holes and re-barrels my share of rifles over the last 40 years. Bores are rarely straight. On rifle blanks, you have to indicate the bore at both end and skim the OD in order to get the bore close to center. Even after, the bore will have a banana. Some worse that others for a variety of reasons. With that in mind, I think the last few inches of the barrel would be where the issues would come about.
I once re-barreled a rifle with a bore that I knew had a banana. I indicated everything within tenths, so I knew the machine work was good. Sighted it in. I then removed the barrel, machined it to index 180 degrees and reshot it. It did exactly what I anticipated.
No direct experience with shotgun barrels but I do know Briley makes eccentric chokes to change POI and they work well. That tells me the last 3" are critical.
I could give other examples with trepanning drill collars over 30 feet, pull bore vs push bore blah blah blah, but I think ya'll get the idea.
YMMV!
Last edited by ithaca1; 05/02/23 12:51 PM.
