Take a machine shop class. Learn to use a mill and a lathe.
Then enroll in a NRA summer gunsmithing program that will teach you hrebarreling a rifle. You should also take gun stocking.
Who knows? You may be our next John Browning. Like Gounard's opera Faust? He used to whistle a tune from that opera.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!