I am not a gunsmith, so sorry for commenting. But I asked this same question a few years ago, and a surprising number of gunsmiths (especially those who specialized in rifle work) gave me the following advice:
Do not think of becoming a "gunsmith." Recognize that a gun is a machine made of metal, and a very complicated and dangerous one. Go to a well-recognized school and become trained and certified as a "machinist." This training will cover everying in general that you will ever need, including blue prints, drawings, measurements, the lathe, drill press, metal craft etc.
Then, go to work as a true machinist in a machine shop for two to three years. (Especially learn the art of the lathe.) If you find that you are good and that you like it, then you are all set with the solid background skills that you will need to become a gunsmith.
Then and only then, go to gunsmithing schools to learn the basics of gunsmithing. The community college in Trinidad, Colorado has many excellent courses during the summer, running from 1 to 2 weeks each, taught by nationally recognized experts, on everything from the most generally rules of gunsmithing to the most detailed type (such as re-barrelling, or rebluing or pistol craft etc.)
After you have taken the basic courses, and the detailed courses in the area that you choose to specialize in, then you are ready to go to work as a gunsmith apprentice.
I just thought that I would pass this along.
Big Paulie