Brass shells are not machined they are pressed in dies very quickly, a very heavy press drops on the dies the impact melts the brass and forces it in to the die form. CNC can make the dies then you need a big press.
Making a gun is easy making a cartridge is not.
They can be machined as well.
Using press dies is great for large runs. Tooling costs, to have the dies made, is very little of the overall cost, though it is expensive for a small run. Having the proggresive stamping presses is the cost of the operation!
For limited runs, CNC is pretty cost effective, just a PITA to get set up so that the case walls are correctly tapered, then they have to be correctly annealed or there will be problems with splits and separations. And the characteristics that make cartridge brass flow very well when run through a press die, somewhat work against decent machining qualities.
There are a couple small outfits supplying machined cases for hard to get rifle calibers.
Be interesting to see if you could put the stretch on some available 16G brass to expand it up to 14.
Cheers
Trev




















































