I'll kill Deer with a pellet gun. Will it work, yep. Will a round ball work on Deer, yep. Is there more bullets that will kill Deer more effectively, yep!!

45 and 50cal muzzleloaders with round balls is terrible. I could definitely see where bigger is better when it comes to round balls. It's a real toss up to what's worse at 75 yards and under between 50cal rounballs and powerbelts.