If the twist is 1 in 66 the round ball is liable to be the only one that shoots good, I have taken 27 deer with round ball most with 54 cal which is the best long range PRB cal. as far as I am concerned, I took a few with 45 and a numer with 50cal. Some people under rate PRB they will do a good job if the shooter does. if you have a 1-48 twist you might try a Real bullet if there are any if they will shoot accurate out of your gun they are a good choice, In the long run the best choice is what shoots the best. Most of the wounding type hit can be traced back to shooters fault, a lot of them do not aim for the right spot or get "buck" fever". I found that right up tight behind the front shoulder half way up the body works well with bow cross bow MZ or high power or pistol taking out both lungs has always done the job very neatly for me. Lee