This subject is of great interest to me. I have been in the tool and die trade since 1979. CNC was in it's infancy then. Back then it was tape fed programs. Allot has changed but it's still the same game. Numbers and commands control it's every move. It's that simple.
I'm gonna back up a bit though. I see a huge problem in our trade. You can go to school and learn all there is to know about making a drawing with CAD and forming a program from that but thats only a start. In cutting metal you have to know what you're dealing with. Is this material something that is easy on tooling and cuts nice or is it the opposite. Fixturing and holding the work is one of the biggest errors I see. That part needs to be held as rigidly as possible and not be distorted either. If you first learn how to cut metal on a manual machine you'll get a feel for things that will help you make good setups on the cnc. Try drilling a 1/2" hole on a manual mill then you'll have a good idea what can be expected on a cnc.
You want to make guns? Okay then. You need to know the best way to make that part. You can make just a few parts and spend allot of time making them or you can make thousands that are virtually the same and make them faster than anyone else. And better too. It takes experience to do that. You have to be able to think that job through from raw material to the final finish it receives. Using a computer and a cnc to make the part. Okay. Do yourself a huge favor and learn how to use and understand g-codes. learn how to edit a program at the machine. Learn how to write one standing there at the machine.
I love this trade. I work in my own shop full time right here at my home. I was fortunate in that I learned my trade from some of the masters of it. Men that had to do things the old school way because that's all they had then. Find some of these guys and take the time to get to know them. You can learn to be a button pusher or you can learn to look at a raw piece of material and see a perfect finished part. The difference between them is like comparing a color between the lines and true art. One of my good friends in business tells me his biggest challenge in finding people to train in his shop is finding that person that can think for themselves.
Here's my website www.crabtreetool.com
Look me up if you like. I hope you grab onto this and become a huge success! We need true craftsman to carry out what is about to be lost. Find some crusty old retired tool maker and start a friendship and you'll be glad you did. Keep me posted on your progress. I am interested. This is my kind of thread!!!!!