What happened here? I found the case on the left at the range the other day. It is a common, Barnaul lacquered steel 7.62x39mm case. Notice how the neck is “stepped”. The case mouth is the same diameter as the normal appearing fired case on the right, but halfway from the case mouth the the shoulder is this step. It seems obvious to me that this case was fire-formed to the chamber of the rifle it was fired in, but the question is what rifle fired it? Is this odd chamber known to be associated with a particular country of origin for 7.62x39mm rifles? It is not a one time fluke thing, as there were dozens and dozens of the exact same cases laying aorund. The funny thing is that sometime earlier this year I read a thread on a firearms forum showing a case just like mine, wondering why it looked this way. This tells me that there are at least TWO 7.62x39mm rifles out there with funny chambers! Any ideas?