I've never used the Kentucky rifle, but I used to hunt with a CVA Hawkens in .50 cal (which was a 1 in 48 twist). The load I used alot was 90 grains of FFFG BP with a 320 grain TC maxi ball (don't know why they called it a "ball"). Anyway, off of sandbags, I was shooting about three inch groups at 100 yards. Longest shot on a deer was a small eight point buck at about 80 yards. Punched right through and the deer ran about fifty yards. Never did recover a slug (shot about 7 or 8 deer with that rig), but it was always bang, deer ran between thirty and fifty yards and fell over (all one shot kills). Hope that helps.