I wish to hunt Cape Buffalo with black powder. I have a Pedersoli .58 cal double rifle. I'm hitting a 2" group at 75 yards with 110 grains of Pyrodex RS. My question is with a 425 grain conical bullet do I have enough gun? Or should I get the .72 cal barrels? I have never hunted Buff and do not want to be a danger to myself or those with me. Because I'm under gunned.