I don't know the twist rate. So far I have loaded modest loads with the 210 cast bullets that should be about 1300 fps, I havent tried them yet. I haven't tried any of the 280's for accuracy.....but I was thinking 30-40 yd max...if they perform out further, that would be great but I wasn't expecting it. I got the 280 Lyman mold for my Whelen, but thought it would be really cool in the max.....with a straight walled case....don't have to worry about seating depth.