So the need for a proof house is really only to protect antiques?
Anything significantly modified, Ben, whether "antique" or not. Remember, the manufacturers already proof test their guns. And they've done so for a very long time. Unfortunately, what they didn't do--going back to the pre-WWII period--was mark all of their guns with chamber length. So, you pick up an LC Smith 16ga and measure the chambers. 2 3/4", so good to go with modern factory ammo, right? Well, someone who really KNOWS Elsies (and that, unfortunately, would not include the vast majority of gunsmiths) would tell you that that gun--if the SN dates it as pre-WWII--almost certainly came from the factory with 2 9/16" chambers, which means metal has been removed from the barrels right where it's most critical, and if you shoot factory ammo, you're now using higher pressure loads than those for which the gun was originally proofed. Maybe you think that's a good situation. I don't.
I have a modern Parker Reproduction 12ga, marked with the chamber length (2 3/4") as are most modern guns. If someone had lengthened those chambers to 3", then that would be another candidate for reproof. In that case, max service pressure is actually the same for both 2 3/4" and 3" 12's, but with metal removed in a critical area, it'd be really nice to have a more scientific opinion on whether the gun is still safe.
