I don't understand the reference to using bulged barrels either. The barrel he made for me certainly wasn't pieced together. I hope he will work with you as he does really good work when he does accept a job. Good luck.
And FWIW, nothing compares to the Thompson in regards to WW II SMGs. Yeah, it's a heavy bitch with a buttstock that was designed for aliens or something, but there is no more iconic subgun for Americans.