My M&P had some issues when i tried to run lead through it. My buddy and i did 1000 lead reloads. I put about 150 of those through the M&P and had 3 really bad jams where the slide wouldn't go fully into battery when it tried to chamber the next round. It took a while to jiggle and jack the slide open. After the 3rd time it happened i haven't tried lead in the M&P since, i stick to jacketed.
Not sure why the M&P didn't like them, the other 850 went straight through a Glock and a Sig without problems. The M&P has been a great gun, and it seems as if other people have ran lead without problems but this was just my experience..... best of luck enjoy reloading!!!