If you are loading for 223/556 make sure you trim them every time you reload. It's easier than taking the time to measure them individually and use CCI # 41 milspec primers.. AR's have floating firing pins and will leave a small indentation on the primer even if they are the correct OAL. If the case is to long or you are using normal primers you are likely to get a double and if the primer is not seated deeply enough you might get an out of battery and total you AR. I have seen this happen more than once. The same precaution should be taken if you are firing your 308's in semi's. only use CCI# 34 milspec primers. An acquaintance of mine blew up his match grade M1A using regular non milspec primers even after he had been warned. He said. "It never happened before"