22.4 grains of 4320 with 77 grain Nosler HPBT's is by far the most accurate load I've found so far in my 223 Ruger American Compact. Its only about 2550 fps (not chrono'd), but if I push harder, the groups open up....I've not got the 75 Amax's to shoot very well yet, but I've been too busy to play around with it much.
