I've tried conicals in my old Rogers and Spencer, both flat base pointed ones using the mold which came with it and REAL bullets of 200 and 250gn from my lee molds for my TC Hawken. They certainly pack more of a punch than round ball and are great for destroyng the target frames as you wont get anywhere near the target with them. Same goes for my Pedersoli pistols. They are designed to use round ball and work best in my experience, with round ball.

Nothing to stop you trying it though.