I've never used Powerbelts either. Not on the range or for hunting. But only because I refuse to pay over a dollar a bullet for what they are. If I were going to lay out that kind of money for bullets it would be for a Barnes.

That said, I believe the game killing performance of a (non-HP) Powerbelt and the game killing performance of a .50 or .54 round ball would be pretty much the same out to 75/80 yards. Beyond that, the PB likely has the advantage due to weight and BC.

If I'm hunting where I expect shots over 75 yards or so I'll use a full bore soft lead conical or a jacketed bullet in a sabot. However, I do love round balls in the right situation. My longest RB kill was a frontal chest shot with a .535 ball at 145 lb. buck at 82 yards. He ran about 40 yards, laid down and died. Still, I hesitated to take the shot at that distance.