Firstly, that's not a safe rifle to fire. It was never designed to handle that kind of pressure and the bore is sized for 22 short, long, and long rifle ammo. The larger bullet diameter of the 22 mag would create a huge rise in pressure. The only way to remove the silver soldered based is to heat them until the solder runs. If it is indeed silver solder I would recommend an acetalene torch to apply the heat. It will produce a lot of heat in a hurry, minimizing the heat transfered to the rifle. If your interested in getting rid of the Lyman send me a PM.... Good luck from the gunnut69