I took my new build to the range for the first time today and fired 40 rounds at 100 yards. It grouped well for the start of the break in period(.75 MOA) but I had 4 rounds where the BCG did not close all the way and had miss fires. I am reloading but have full length sized all of the brass with new dies. The upper is a DPMS 24" fluted bull barrel. Are there any sugestions on a fix to this intermitant problem?