Are you using small rifle primers? I keep seeing mixed reports whether to use small rifle or small pistol.
While I have seen some load posted in the occasional gun magazine with loads worked up with small pistol primers, there's only on REAL source for the cartridge, and that source is Federal/Speer. Techs at ATK ensure that this round is only ever factory loaded with small rifle primers.
With a max chamber pressure of 45,000 PSI, small rifle primers are a must, and pass the word to anyone handloading it that it's spec'd for small rifle primers.