Some 9 twist shoot the 75 amax and some don't I had one of each. but on all my large bullet 223 loads I learned long ago that powders like rl15, varget V.V.540 and 550 are the way to go, I also found that I had to push the envelope to get the best accuracy RL 15 and 540 seem to shoot best right before you cross the don't go here line. that line is different in each gun.