The manual that came with my new M&P 15 contained multiple warnings about only using ammo with non-corrosive primers. I just got a pretty good deal on some PMC X-TAC 5.56 rounds, but can't find a reference to the type of primers in these rounds.
I think you're good. They seem to be non-corrosive boxer primed rounds made in Korea. Apparently decent quality stuff from what I've read - even though I have a cousin who claims PMC stands for Pretty Much ****.
All PMC Ammunition is loaded in new brass cases with boxer primers. PMC ammunition is non-corrosive and is loaded to SAAMI specifications with the exception of 50A, 5.56X and 5.56K. Each of these rounds complies with US MIL. spec.
PMC is my favorite factory ammo to shoot. So far I have shot the 9mm, .223 and the .308 and have zero issues with it. It shoots cleanly and accurately.