I used to have two books, Pistolsmithing by G Nonte and Gunsmithing by R Dunlap.

Both had many, many things that could be done with simple hand tools, including fitting a barrel to a rifle or pistol. They are worth what you will pay for them if you want to work on guns. Nonte's book, since it was written back before plastic guns, concentrated mostly on the 1911 and revolvers.

Dunlap's book was before the black gun so concentrated on the bolt guns, especially surplus, and the Garand. The many methods of cutting and crowning a barrel are in there. Also all the methods of bending/shaping/welding bolt handles for different looks or to clear scopes.