I had a couple of Thompson Center .50 cal. Hawkins rifles that shot well with both conicals or patched round balls. In fact, the first shot better with swaged patched balls than any conical bullet I tried. I could usually have 5 shots touching at 50-60 yds. Beyond that, the limiting factor was the open sights with a front bead that covered most of a deer's chest at 100 yds. But even at that, I could easily stay well inside 3 inches at 100 yds which is much better than minute of lung. Peep sights were not legal for our flintlock deer hunting, so I made some modifications to make more precise shooting possible, and still remain legal. For some reason, we had to use round balls too, and I remain very impressed with the performance of them on deer. As Stan said, penetration could be very good due to the momentum of a blob of lead. Of course, hitting bone flattened them out nearly like a half dollar, and they would often be found under the hide on the off side of a deer. Actually, penetration will often be better at lower velocity because the soft lead ball doesn't expand as much in flesh.
I had a .69 cal.percussion musket for a time. It was a blast to shoot with round balls and 160 gr. FFG powder. I was probably using much more powder than necessary, but I was young and using the load the guy I bought it from used. The accuracy was not very good, so it went down the road. Recoil was impressive, but it was more of a long shove than a sharp jolt.
