Ok, I've been reloading for a long time and just ran into a problem. I have 2 new Rockriver AR-15 and made up some reloads for them. I went out to shoot and one chambered and fired a 30rnd mag. The other would not close the bolt on the same ammo. I had to pry it out. I took each reload and when dropped into the chamber would not go all the way in. I dropped the same reloads in my bolt action .223 and it fit like a glove. Some old Lake City mil surp chambered also. Question, I full length resized all the cases and they were once fired Lake City. Headspace problem? Small base problem? Tight chamber problem? what?