Finally got my lightweight AR out and shot. Went through 120 LC M193 and 30 75gr Hornady TAP on Sunday. Of the 150 rounds, I had three failures to fire, two with the M193 and one with the TAP. BCM upper receiver, CMMG pencil barrel, and LMT FA BCG. The rounds were dimpled by the firing pin but not cratered like they should have been. Any ideas what caused the failures or what I should look for?