Quick question: I just put together my first build. When I brought it to the range today, I shot 55 grain, Tactical TRU, by Federal Premium. The rifle shot a 1” group at 75 yards. That being said, I have a slight problem. When using brand new 30 round P-mags, the bolt fails to remain open on the last shot. I shot four different P-Mags, all with the same problem. So, for shits and giggles, I shot the same ammunition through a couple of regular (metallic) USGI magazine. After the last round, the bolt DID stay open. Any ideas?
My setup is as follows:
Spikes lower w/DPMS LPK installed
Magpul CTR butt stock w/mil spec tube
Spikes 16” M4 complete upper w/7” DD lite rail (free floated)
Magpul MIAD full grip kit
Brand new Magpul 30 round P-Mags
P.S. I am VERY HAPPY SPIKES!!!!!