I just took two new 308s built on Defiance actions and Benchmark barrels shooting last weekend and out of 60 rounds, same lot number, of Federal GM ammo, 2 would not chamber. I disassembled them after measuring headspace, bumped the shoulder back 2 thousandths, and reloaded them just so they'd fit. With the belted cases, it's my experience that most will grow significantly in the chamber. Just another reason to fireform all brass to the chamber. Curiously, I've still seen quite a bit of factory ammo shoot extremely well despite the excessive headspace
Fire formed brass, shoulder moves foward, headspace off shoulder once-twice fired?? Headpace off the belt for your choice of brass and its belt?? I'm kinda mixed up
