i started out using 777 and quickly determined it sucks in my gun. i gave what i had left away and bought pyrodex. that in itself tightened my groups up by 50%-70%. like i said, i tried 100 grains and wasn't happy. the powerbelts shoot great on paper in front of 150 grains but don't hold together when in contact with meat. maybe heavier powerbelts? after all i was only shooting 245 grain aero tips