Just to add a few comments to what I've already written - my .54 flintlock is a slow twist barrel, and though I only mentioned the Buffalo Bullet Ball-ets, It does shoot really well with patched roundball loads, both .530 and .535 with appropriately tight patches. I've got a round ball barrel T/C Hawken Target (30" barrel, blued steel furniture, tang ladder type peep and globe front sight) that shoots ONLY roundballs well. Ball-ets in .50 caliber don't stabilize at all in that gun, but man does a .495 roundball go straight. I've shot woodchucks at 125 yards (farthest shot with that gun) and it is instant death with anywhere near a good shot. I've never had a chuck hit with it that even did the tail wiggle. In addition, it has killed about 10 deer, all but one were one shot kills, and the one that required two shots was absolutely user error.
I don't know what the caliber of the originator of this thread had in his GPR, as he doesn't say, nor why he doesn't want to mess with patched balls. I've known people who believed that patched balls were too slow to reload when hunting, but speedloaders cure that ill, though frankly, the suggestion of a ball block may well be the fastest reload of all, with easier centering of the ball, etc. and a well lubed ball will make cleaning easier, in my opinion than the conical with it's possibility of leading, and the sabot with the strings of plastic left behind. By the way, a teakettle full of boiling water, will clean out that plastic like magic. It comes out in nasty strings, but it does come out.
It does make sense I suspect to shoot a conical or a REALLY big roundball when hunting bears, elk or moose, but for most hunting, deer on down, at the ranges a muzzleloader is genuinely best at, a round ball will get the job done in my experience.
If you want a 200+ yard gun, you're really talking a different game, and T/C or any of the others will sell you something that will suffice. For fun? The round ball gun is an absolute delight. For typical hunting? The roundball will get the job done. For style? Personally, a side hammer gun makes me feel more like Daniel Boone. (Yes I realize that in lines in some form have been around almost as long.) Just some rambling thoughts.
Jamie