I currently have two smooth bore muzzleloaders, although only one has any semblance of tradition. The first is a Knight TK2000, an inline 12 gauge with screw on jug choke. I believe it was the 3rd gun I ever bought in my life, a spur of the moment buy from a gun shop, years before I had any real interest in muzzleloaders. I bought it for $110 that day, best buy I ever made. This gun was made to do one thing, hunt turkeys. As such, I've never fired anything but shot from it, and have taken a number of turkeys with it.
The other I have is a Pedersoli SXS 10 gauge. Well, it's an old one, and in reality it is an 11 gauge with .764" bores. Both barrels are cylinder bore, no choke. This is a recent gun to me, I spent all spring trying to get it ready for turkey season. It took a monumental effort, but with 2 ounces of #6 shot, some good ideas from fine members online including this one, I was able to get an effective pattern to 25 yards. I don't care what anyone says, that is no small feat for a cylinder bore unless you are willing to chance a less effective pattern. My minimum is 100 pellets in a 10" circle, and I was only barely able to meet that. I ended up shooting two rabbits as well, and quite a few clay targets.
I've always been a shotgun guy, never cared as much about rifles. It's no different if I'm loading from the muzzle. One of the reasons why is the versatility. So in this Pedersoli, I have been playing with both bare and patched round ball. As far as I'm concerned, slugs (or balls) are just as common to a shotgun, as they are to a rifle. If I had to guess, buckshot was used much more in the past than people realize. It is a most effective round. With my Pedersoli, I can load .380" buckshot with ease, and get pattern I would use on a deer to 35 yards. While I'm able to get groups good enough for 50-60 yard shots with a single round ball, unfortunately the barrels are not perfectly regulated, and neither one is perfect to the bead. So I can have buckshot, which is the most effective choice on medium game used within its limits, in this case 35 yards, and with a pattern that makes shooting moving deer a breeze. Or I could use a singe round ball, which in this gun would be a 40 yard or so deal, and is much more dependent on me making a perfect shot. Unfortunately the bureaucrats have made the choice for me in my state, and I am required to use the single round ball. A shotgun, used as a shotgun, is an absolutely wonderful thing.