I bought my M&P in part because I'd heard they will eat most anything you feed them. Indeed, my used 40c has never once complained about any of the cheap aluminum case junk I've run through it. It has been 100% reliable! So I bought 4 boxes of Perfecta 170 gr FMJ at Wal-Mart. I wish I had tried a box first, because the first box resulted in at least 25% or 30% failures to feed. Even on racking the slide on the first round of a mag. Due to their no return or exchange policy on ammo, I am stuck with 3 more boxes. I saw mostly positive feedback on a thread in the Ammo Forum but I didn't read through all 3 pages. Oh well, live and learn.