hmmm
I would need to do some looking but there was an article a few years back where the author was talking about barrel making and long range accuracy. They had access to a large empty warehouse where they set up their range in order to eliminate wind etc... In the end they took a length of rebar and bore and rifled it installed I on a receiver and shot it just to prove that they could make a precision barrel out of anything.
Rebar eh?
all those ridges would be like fins on a radiator, great for cooling! lol