I am prepared for all the jokes. Fire away.
I have an under hammer. I got a very nice 20ga barrel. When installing the nipple I put it in 1/2 a nipple too far away.
In the antique motor hobby you just plug the hole with a bolt. Fix it in with green loc-tite. And drill a new hole.
I have a shorter nipple on order, but can you plug and re drill?
Lost