300 BLK loaded with AA #9, thoughts from the lab... Using data for .357 SIG Bullet weight, 145 grains, max pressure, 33,000 PSI, velocity = 1170, charge weight between 9.4 ~ 10.5 Using data for .357 Magnum Bullet weight, 150 grains, max pressure, 33,540 PSI, velocity = 1394, charge weight between 12.6 ~ 14.0 Using data for 10MM Bullet weight, 155 grains, max pressure, 32,700 PSI, velocity = 1414, charge weight between 14.3 ~ 15.9 Quote from "300 Blackout talk Forum": "...I tried 16.0 grs and 17 grs of AA#9 with a 150 gr FMJ. I was using formed brass. I blew two primers out . The primer pockets were expanded so that a primer would not even seat anymore. So I pulled the rest of them. I know it will run with 125 gr bullets as the data was published in the most recent Guns and Ammo issue. My fault I suppose..." So, it looks like, to me, that we start with a chronograph, a target and loads beginning with 14.0 grains of AA#9 and work our way up? Somewhere between 14.0 ~ 15.8 grains should be the desired end state, the barrel length (16.5 inches and beefier chamber OD vice a pistol barrel OD should contain the pressure. Accurate published max pressure for AA#1680, in an AR (16 inch M4 barrel) at 54,564 PSI for a 150 grain projectile. I can't seem to find any comparison data on burn rate. What do you think?