..I would think that round balls should fair somewhat better than conicals, but hard info beats guessing.
Tom,
Think about this for a second. If you shoot a round ball from a smooth bore barrel, you are shooting a musket. If you shoot a round ball from a rifled barrel you are shooting a rifle. The early muskets were often shot with out patching during war to save time loading. Hence the need for long lines of shooters facing each other.
When I did a lot of black powder rifle, the trick to accuracy was properly patching the ball so it engaged the rifling and prevented any blow by. The rifled shotgun slug was developed to help stabilize the slug by imparting spin. The skirt expands to prevent blow by. The minie ball kept the skirt in the design for the same reasons.
It sounds like your slug is not being stabilized, hence the large groups down range. A black powder rifle shooter with a decent gun can eventually work up a round ball load with patching that can achieve 1/2" groups at 100 yards.
