You need a Rugar Black Powder. By far the best.
Use the conical Bullet, it work the best I have taken deer out to 40 yds with mine. One of the reasons it is better is because of its accuracy, I tried a bunch of those replica ones before I tried the Rugar the accuracy I got with them at 50 yds was deplorable, as well as the fact I spent about as much time fixing them as I did shooting them.