I once saw a model 1911 pistol completely made by hand by some Viet Cong craftsman. The slide release, safety, recoil spring plug, barrel bushing, sights, etc, were all one piece and just carved in the metal. Lots of file marks all over. The pistol was "sway-backed" from being fired many times -- the steel was too soft to stand up to the abuse. At the University of Alaska museum in Fairbanks they have (or did) a hand-made copy of a Ross rifle in .280. As I recall, some guy named (Williams?)invented and manufactured a gas operated rifle in his prison cell which was later sold to Remington. So... given a piece of railroad track, a hacksaw, a Chinese milling machine (a mill bastard file), and something to drill and rifle the barrel, it can be done by anyone with some mechanical aptitude and a whole lot of patience.