So first off I apologize to the big m&p guys for my newbie ignorance with m&P's. I'm a bolt action guy and I only got this for personal projection. Now supposedly this thing has been rebuilt from the ground up and it came with a threaded 9mm barrel and a standard .40 cal barrel that I can swap and it allows me (obviously) to change rounds with ease. Now being ignorant to hand guns and their respective calibers... I bought 9mm Lugar +P+ ammo and in complete ignorance fired off two 17 round mags off. On my second purchase I received a warning that +P+ might be dangerous with my m&p. So I then researched as much as I could however, I could not get an answer to one single questions. So here it is... If my m&p can fire both 9mm Lugar and .40 cal with just a simple switch if the barrel; then is it really bad for my specific m&p to fire 9mm +p+ ammo given that it is obviously higher combustion however I am not confident that 9mm +p+ is a higher combustion than the .40 federal ammo... Any information would be greatly appreciated.