I have a 54 cal with a 1/66 twist that I exclusively use with prb and out to a 100 yards I have never lost a deer or had to track one very far. I shoot a 100 gr of powder and a remington #11 cap. It will stop anything in its tracks .The most important thing is enough practice to know where you will hit that sucker. The round ball sheds energy fast but will take a deer down at 100 yards easy.