.457 round ball. Using 11 gr. Unique no filler. I haven't taken a picture of it yet, but I've added a thermal receipt paper wrap that seems to get the rifling better like a wad on a round ball with a muzzle loader. If I can I will take pictures of my next batch. I use the Lee Expander die to set the balls in place, so they are the same each time. It should be in just past the hemisphereical equator and then use a Lee factory crimp die to lock in place. Without the paper, these average 2-3" at 50 yards, although I hit a woodchuck at almost 100 yards with one. I have tried from 6 gr. Unique to 15 and at 6 gr. the ball rolls out the end of the barrel. lol kinda funny.
at about 13 you get leading, so I have backed down to 10 or 11 gr. as a pretty accurate range. Paper has tightened up the group a bit and probably let me get a little more velocity, but these are all about having fun plinking, but I carry a few when deer hunting for small game opportunities.
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One quick thought though, if you are shooting from a short barrel, 6 to 10 would be a good start range. Lot less drag than my 32" on my BC.