My short answer to the 2.5 vs 2 3/4 chamber lengths....I don't know. I find it difficult to not believe pressure tests. I'm also not going to shoot 2 3/4 shells in any of my old guns whether it's safe or not. What I do know is part of the romance of the older guns that appeals to me is their short chambers but, I'm a bit of a romantic at heart. Much preferring to go to the effort to shoot in it what a firearm was designed for. For a long time, long before 2 1/2 in. shells were again available, I've been cutting back 2 3/4 hulls to 2 1/2 length and roll crimping them with an OSC. Why go to all that trouble if 2 3/4 shells will work? Because that's what the chamber was cut for, I enjoy doing it and they work just fine for any application I have for a shotgun. That and I am not about to have the chamber lengthened on any of my old German guns. I did that with my first drilling nearly 30 years ago and regretted it ever since. Had I known at the time how easy it is to make 2 1/2 in shells it never would have happened.
The argument over Damascus barrels is similar. Old wives tales say one thing, pressure tests another.
With my home rolled shells it's also kind of fun when youngsters, that's anyone under the age of about 40-45, look at my shells and question the OSC and a roll crimp. "Where did you get those" is a common question. Or, "I've never seen anything like that". 'Course, I get that a lot, whether shotgun or rifle and the ammo for either.
