Shelton, I'm reloading and almost identical load for my AR15. It groups great, but I was getting the same flat primers with mine from the starting load all the way up to 25.5 grains where I found the sweet spot. I was using CCI small rifle primers remington brass. I switched to Winchester magnum small rifle primers on the recommendation of a friend and reworked my load up. It fixed the problem.
I'm not a master reloader, pretty new to the game, so I don't know if this is common or not, but it worked well for me. Supposedly the magnum primers have a thicker wall and don't deform as easy. The reloads shot great with both set ups, but I feel better about the primers not being so deformed.