If you are just out to have fun, punching paper targets, nothing is as nice as a patched round ball. It is sparing of both powder and lead, and very easy to load.
Despite the fast 1:38 twist, my .50 caliber White Mountain Carbine shoots round balls quite well. Thompson Center may have intended it for heavy charges under a conical Maxi-Ball, but light loads of 3Fg deliver the goods:
2.8 to 3.1 cc of 3Fg Schuetzen propel a patched round ball, loaded over a felt wad, to around 1,000 fps. There is no noticeable recoil, just a bright flash and big cloud of smoke.
These targets were shot at 25 yards, with the open iron sights. My elbows were rested on a bench, with no other support.
The trajectory is pretty flat to 40, but there is a rapid drop beyond that.
Round balls are notorious for ricochet, so do pay attention to your backstop! At 40 yards, they retain more energy than most .38 Special revolver loads at the muzzle.