I had a Lt Colonel friend who bought one with the chamber hogged out like that, someone's idea of deactivation. Someone else tried to restore it by soldering in a piece of steel with a Kragchamber cut in it. It was blowing gas every time he shot it. I think that one was bored shallower than what yours is, but past the end of a normal chamber. He was taking a gunsmith course, so I sold him a decent original barrel to put on it.