The barrel has definitely been replaced, an unmolested rivet looks nothing like that. As far as the barrel being serial numbered, the number on the barrel is a production lot number from the steel factory. It is not a serial number, and it should NOT match the guns serial number. The only thing I don't like about an MP44 is holy crap that thing is heavy, it really makes you appreciate what the german stubble hoppers had to go through lugging that thing and running from the Ivans . The guy I really feel sorry for though was the one that had to carry the Lafette tripod slung on his back in a HMG crew. Wow, they must have had to draw straws for that assignment.