I have had an unusual malfunction in an almost new Daniel Defense DDM4 V7. The rifle functions and shoots very well, except for one thing: on some Magpul PMAGS, the bolt fails to lock open after the last shot. I had thought it might be an ammo issue, but on the last trip to the range, trying several different magazines, it only did this on one kind, the MOE M2 PMAGS. My old PMAGs with no MOE markings work fine, as well as the newer MOE M3 mag. Just not the M2...thankfully I don't have very many of the offenders. Guess they will just be used in the S&W M&P15 that doesn't care which mags it uses. Just wondered if anyone else has seen this with Daniel Defense rifles.

Don't own a DD, but my Daewoo K2 does likewise with M2 P-mags. Don't drop mags from airplanes or roll over them with tanks, so prefer alloy USGI to P-mags. Bolt always stays back after last round. Like the Colt/Okay/NHMTG mags best of all.