The answer could lie in the twist of your barrel. If it is 1-48, it should handle conicals well, if it is slower, then it is more of a round ball gun. I once owned a TC .54 (1-48 twist), and now own several Lyman's in .54, a percussion cap and a flint model. The flint model is a 1-77 gun, strictly for ball loads. The other is 1-48, and will handle both balls and conicals. My best accuracy has been with Lyman Great Plains Bullets (a hollow base conical, 425 grains, I believe) behind 100 grains by volume of Pyrodex RS powder. No problems keeping five shots on a paper plate at 100 yards. This load has accounted for a number of big bucks, and hits with authority. Round balls with similar powder charges will also work quite well on deer, though seem to hit with a little less "smack" then the big conicals, or at least it seems so on the PA deer I have taken using ball loads before conicals were legalized here.
Like any rifle, experimenting with bullet weight and charge weight can make a big difference in accuracy.
Larry