[Chode]

the barrel is the hard part, the rest any competent machinist can do

[marktwain]

Exactly correct.

I think most welders in the United States would do a better job on the welding.

[wrench]

With the barrel having a taper, it came from another weapon. Heavy machineguns have quick change barrels, most likely where this barrel originated. As crude as the rest of the gun is, the barrel stands out as being a manufactured part.