First time firing a new barrel. I didn't see any grooves in the bullet when I cycled them before firing.
But great suggestions, TY.
All my AI 30 cal barrels HATE Hornady bullets. I was popping primers at 2550 fps with 308 178 BTHP rounds. I even pulled down FGMM 175 rounds which shot at 2700 just fine and put the 178 in making sure to not touch the lands. It was still overpressure by a massive amount.
I have no idea why, but it is consistent across guns, barrels from both Bartlein and LW, and across OAL variances, charges, and case type.
The ONLY thing it could be is the bullet. I have seen this in 30-06 with Hornady 208s as well.