I ran into some "weak" 40 SW brass, ball ammo, first shot, The M&P ripped the head off, case fell out, bullet hit the target, and mag was blown out. ( first time firing the gun, I thought I had not pushed the mag in tightly) case head "ejected". There was multiple cases on the ground so I did not notice one torn up. Re inserted the mag, fired the second shot, same except the head case was stuck in barrel. I removed the case, emptied the mag, disassembled the gun and mag, nothing appeared broken/damaged. I reloaded a different mag with different ammo, gun fired fine, ejected intact case, but mag dropped. Did it occur from the first bad round? Which was the first time I had ever fired this or any other M&P. ( I thought this might be a S&W speed training drill- fire, retrieve mag, repeat times 16!! ). S&W CS was going to send me a mag catch, but I sent it in to be replaced and "checked". They replaced mag catch, no further problems, as for the ammo , it was set on the side, broke down, 10 charges/ bullets weighed, with in spec. Consulted someone who knew more about the loads, and I found out about some 40 S&WBrass that had been damaged due to cleaner used, ( 2005-2006 ?) apparently - most/all had been destroyed- OOPS!!.. Have not had a problem since. I bought one of the 357 sig M&P yesterday. Be Safe,