I dinked with "buckshot" in a 62 cal and a Bess- actually it was .310 shot in the 62 and .350 in the Bess. In the 62 it worked out that four layers of 3 shot each (total 12) was best. In the Bess I thought I could go six layers of 3, but actually got better patterns with 5 layers, or a total of 15.
"Best" is relative. I got patterns with the 62 that I'd use to 20 yards, max 25 yards. In the Bess I'd go 30 yards and no further.
Best combos in both featured a lubed Type A card under the shot and a pair of overshot cards on top, and as much corn meal as I could vibrate down among the shot. Total loading time after arranging the shot as you loaded, adding corn meal and all was somewhere north of 5 minutes per load.
Saying all that, a bud of mine is kind of a buckshot specialist with his modern gun. He grew up in an area that required it, so fully appreciates its range limits. He loads his own using hardened 000 buck, poly filler and just the right choke. With his best performing loads ( 3 1/2" 12 gauge) and a whole lot of pattern testing, he says he can reliably put at least three shot into the chest of a buck at 40 yards. He therefore limits his shooting to 35 yards.
BTW- I used his 3 shot in the vitals as a standard for rating my own loads. He was quit impressed with the range I got with the two muzzleloaders, but I wasn't. He won't hunt with the ML because of the reload time. He's pretty quick to shuck another round off after the first shot to limit trailing distance. Ain't a possibility with a ML unless you're shooting a double.