I know: Necro-posting!
But, I am having the same issue on my 1953 [ish] Polish M44. I am getting a longitudinal mark/crack on the neck of my shells after firing. On steel is is a very light crack. On brass it is a scratch/divot.
Has anyone read anything about the Com-Block making military weapons so that they mark the shell when being fired, and the brass is thus identifiable [and un-reloadable]?
I thought I'd read that about AKs or something, but I can't track the thread down.
So, was there any solution to this issue? Or did the gun blow up?
I'd like to know before mine blows up!