By the late 19th Century, companies like Winchester had their piece-worked parts spec'd out closely enough to achieve almost total interchangeability. For instance, you can still take an unaltered high wall barrel from one rifle and have a high likelihood that it will clock up correctly on another, unaltered, receiver. If they could do this by hand 125 years or more ago, it should be achievable with modern technology such as CNC & CAM, wouldn't you think?

Froggie