@Cave Troll It wouldn't be an ideal situation, but a machinist could continue the process of forming the bullet. A cap is stamped out of a sheet of metal, the cap is heat treated and stretched into the full casing shape. A .45 casing could be compressed, stretched, and cut down to a .35. I mean, we are talking about the nonexistence of firearms and ammunition, of manufacturing processes for 50 years. It could be a situation where there are hundreds of thousands of rounds for a dozen existing rifles, and zero rounds for 150 newly built rifles. Melting the casings down would mean the need for a stamp to make the new bullets. New rounds require a complete creation process. Old rounds could only require a portion of it.