Not sure where you heard a CNC was needed, but a gunsmith friend of mine (he served a traditional apprenticeship) once told me that everything that a mill does, can be done by hand. It will take a lot longer, and requires a lot of skill, but guns have been around far longer than DRO's and CNC machines.My newest accessory I just purchased is a 6" Grizzly rotary table.
I am trying to establish myself as a gunsmith, and one of the things that I would like to get into is slide cuts for red dot sights. I was under the assumption that I would have to bite the bullet and purchase a CNC mill to handle a job like that. Then I found an internet forum post that outlined how they made it work with a manual mill and the rotary table. Which saved me about 20 thousand dollars, lol.
I've also invested in the factory installed DRO, and a X-axis power feed for my PM-25