I had a 1912 20ga flues in otherwise 95+% condition that had 2-15/16” chambers. Also a 30” 20ga flues with 2-15/16” chambers, but it’s condition was much lower and I can’t be as sure it wasn't modified. I know of one other very high grade 20ga flues with almost 3” chambers.

Also, the high condition gun had a “2nd” marked on the barrel lug with no obvious variation from a standard gun other than the chamber length.

Last edited by bsteele; 09/14/21 05:29 PM.