Generally the slower twist rifling does not stabilize long bullets well. That 1:72 ROT is designed for use solely with round ball. Now, the more commone 1:48 is a compromise ROT, in that ie will work fairly well with round ball in .45, 50, and 54 caliber guns, and it will ALSO shoot short conicals, such as the Lee, Real ballets. If you start adding length to a bullet, you need to use a barrel with a faster rate of twist to stabilize it. For a reference, the .50-70 cartridge, and the .45-70 cartrides, shooting 500 grain bullets, had barrels with a 1:22 ROT. Target shooters today, shooting those same calibers, generally prefer an even faster rate of twist, namely 1:16 or 1:18.
I would only suggest that you not try to make your gun do something it is not designed to do. If you have a slow Rate of Twist(ROT) then leave it as a round ball gun. A round ball is an incredibly efficient projetile for killing game. Just read all the posts under " hunting ", below. Modern shooters, used to jacketed bullets, and smokeless powder cartridges, have a difficult time accepting that, simply because pure lead balls, pushed by Black Powder is an entirely different system. The human brain wants to relate things to what it already knows, and does not accept changes well. In this case, you need to trust in the thousands of testimonials, and the dozens that appear on this forum from members telling you how quickly deer drop when hit with a round ball. Almost all the members here have had prior experience shooting modern guns, and many have taken big game with them as well. All will admit being impressed with how effective a round lead ball can be in the field after their first BP kill. Me, too.
