From Lyman's "Black Powder Handbook", first edition: .50 cal., .495 ball, GO 3F powder, 32" barrel, 50 grains gives about 1450 fps and 85 grains about 1800 fps. With 50 yard zeroes, 50 grains drops 55 inches below point of aim at 200 yards and 85 grains drops 40 inches. With only 5 mph of wind, EACH drifts about 21 inches. I have shot my .54 at 100 and then 200 yards and the wind really moves that ball. These figures are bound to give you a big advantage over other shooters that haven't actually shot at 200 yards, because few people are into ballistics enough to know them. Use either load, but practice what 40 or 55 inches of holdover is at 200 yards.
I was in a shooting contest years ago where we'd start at 100 yards and the winners backed up about 25 yards. I was back about 200- 225 yards with Doc Gary White of the old Green River Rifle Works, having to guess how high to hold my .45 Green River Leman. He beat me. I didn't have any experience at that range. So, win that ham!