The maker of my Hawken(Investarm) says that the max load for it is 90 grains with .490 ball or 80 grains with a 370 grain conical. I have shot 80 grains behind a 240 grain conical a few times but not enough to see what load is accurate, if any. I have never shot a round ball thru it. It is a slow twist, about one in 60 or 66 as best as I can measure it, and is 15/16 inch across the flats. Seems to me that it should be able to stand more powder, TC says 110 grains max behind RB for the same barrel size. The gun is better looking then the TC Hawken, or I would trade it off.