.54 would be ok. I cast my own balls (sounds kinda funny saying it out loud) so .54 would be alright. The biggest game I go after is Northern Whitetails, they get pretty big but nothing a .50 or .54 round ball couldn't handle at 100 yards. This is the first 1 in 48 I have owned and even tho it's pretty I am not happy with the way it shoots. Over the last 10 years I have put about every conceivable combination of powder and projectile threw it and have never been able to get better then a 8 inch group at 100 yard off a bench. Good enough for hunting around here, but should be way better. I'm not always hunting when I shoot it.