In ALL of my fast twist 223s, I have found that the BTHP to be more accurate than the 75 A Max.... but the 80 A Max is an accurate as the BTHP....
didn't matter if the velocity was fast or slower than max...
YMMV...
Saw the same in my 223AI and 223 Tikka. As good as the 75 Amax was/is, the 80 Amax was/is better.
