I have tried both the SST's in 250gr and 300gr and can't get either to shoot under 3.5" groups at 100 yards with pyrodex, or 777 from 90gr to 150gr. But everyone else and all I have read seems to be getting great accuracy. This is out of two different muzzleloaders that shoots 250gr Barnes and 240gr XTP 2" groups at 100 yards. I can't figure it out. I am using the special attachment that is made for the powerbelts too.