I think two major areas of expertise are required and you have one covered. Having the ability to make or modify the hardware puts you ahead of most, but until you have an in-depth understanding of how a large variety of guns work, you won't know how to apply your machining skills to the problem at hand. Finding gunsmithing classes at a local community college would be a good start. Apprenticing with a successful gunsmith would be better. Both would be ideal.
Yup.... gunna need a milling machine. Wish I still had my Tree mill.
