If you make a chamber cast you will likely find out that a cartridge with a bullet that big seated in it won't chamber anyway. With that rifle, you pretty much have two choices as to what bullets to use. Either use .379 or whatever will safely chamber, cast out of 20:1 lead/tin or softer and of course loaded with black powder. It will slug up and seal the bore as long as it's soft enough and doesnt have any antimony in it. Or you can use pure lead or close to it paper patched bullets, set up to bore diameter or just a hair above. Again, BP only. Conventional groove size lubricated cast bullets, made hard, are not going to work in this fine old rifle. If you feed it what it was designed for, you will have good results. Otherwise you're going to have a tough time making it work.
