If you think a 9 twist is going to stabilize a 75 Greiner in a 223 you better live on top of a very tall Hill
I have a Stevens 200 .223 with a 1/9 twist which is stabilize a 75 gr Hornady HPBT out to 500 yards with authority at 500' ASL. That same barrel won't stabilize a 75 gr AMAX at 100 yards. It's all about the length of the bullet as well as weight.
Crazy as it sounds, I have a Tikka .223 1/10 twist which will stabilize the same Hornady 75 gr HPBT bullet at 100 yards. I have not shot it at distance but it was able to give me < 1 MOA groups @ 100 yds. I have not measured the barrel twist to verify the 1/10 that's stamped on the barrel. It also stabilizes 69 gr SMKs out to 500 yards.
