Go to your local technical school and learn how to use a lathe. You will be miles ahead when and if you decide on a school. Building a rifle is basically facing, boring, and threading. You will learn that in your first class. You will also learn whether or not you have the patience for "percision" work. Few people have it...and of those who do, many find that they cannot maintain the drive for it.
A lot of community colleges have machine tool technology (MTT) classes.
