I have never had that problem either Pmags or brass cased ammo. I had a Bear steel case round that was jammed so tight the range officer had to take a rubber mallet hitting my charging handle to free. That was with an older generation M&P MOE. He knew exactly what to do and said is pretty common with a Russian ammo. I know this is a little off subject, but I have to think most causes of AR jams are either ammo or dirty chamber related.
I assume it was the cheap Russian steel case ammo so I gave what I had away and bought a BCM charging handle in case the original was bent. Just as a precaution, you might want make sure your charging handle is not bent.