The standard profile barrel and the ribbed target barrel are both, AFAIK, made from forgings. To machine one from a cylindrical barrel blank would not be practical. Even for the basic barrel, one would have to deal with the locking lug under the barrel and somehow provide the front sight base. Not so simple for even an accomplished machinist.

You would be much more likely to succeed by starting with a pre existing barrel and rebore or reline it where possible to achieve the desired bore. Trust me, this is something to which I have devoted a great deal of thought and research. I would happily accept any new information and technical strategies, but I haven't seen any lately.

Froggie