I’ve shot tens of thousands of 2 3/4” handloaded ammunition in my 2 1/2” chambered guns with no ill effects. And most of these have been in damascus barreled guns. But I do load with pressures the guns were originally intended for. Velocities are kept between 1100 to 1200 fps and pressures (as published) below 8,000 psi, usually in the 7,000 psi range. As long as the hull does not open into the bore but stays in the forcing cone all should be fine. As Drew mentioned above if the mouth of the fired hull is ragged it is probably opening up into the bore. Frankly, I have never had this happen.
Pressures drop of dramatically after the shot leaves the chamber. The most important wall thickness, in my opinion, is immediately in front of the forcing cone. I’ve never found a consensus of opinion of what the minimum should be in this area but I like a lot, say near .100”, sometimes a little less. Many factory guns were made with them even thinner and I shoot some…..but then, I’m a grown up boy and do it heads up.
