Buy some FFF Goex and some 250g Shockwave bullets for that rifle. Use between 80-90g of the stuff and you will be surprized. Some of the best targets I have ever printed came from my Scout. If you have a reloading shop near by look for the Hornaday 265g flatpointed interlocks, they are one of the best all round bullets I have ever shot out of a muzzleloader. They are .429 in diameter and shoot quite well with the loose mag-express T/C sabots you can buy at almost all gun shops.

I bought those bullets for reloading my .44mag and ended up shooting them in my m/l instead