No home hobby machine shop can produce a rifled barrel.
I have much of the tooling from an old gunsmith who died in the 80s. There are many rifling buttons he made for most any caliber. It is totally possible to make your own rifled barrels.
And there is no need for a CNC mill to make guns, a manual Bridgeport will do just fine. ;)
I was in Jonathan Brownings workshop in Old Nauvoo (father of John Browning) in August, the rifling of barrels was accomplished quite easily in the 1840’s with a wooden screw tool pulling a carbide cutting piece repeatedly through the barrel... The barrels themselves were formed from FLAT steel hammered into half round forms.
I beg to differ. Boring the barrel takes some technique, but if they can do it in Darra Adam Kel in the tribal territories in Pakistan, or if backwoods gunsmiths could do it in early 1800's Pennsylvania, hobby machine shops with precise lathes can do it easier.