My M&P 40 FS will fail to feed 180gr FMJ .40s&w once or twice a magazine. Sometimes I can tap the back of the slide to put it into battery and sometimes I have to eject the mag then pull the slide back to clear the malfunction. The ammo used was always brass cased and from various manufacturers (WWB, UMC, Blazer, etc.)
The first time I took it out I put 50 rounds of WWB 180gr down range with no problems but after that every trip to the range resulted in the malfunction I mentioned previously. I never contacted S&W about it because it was never a CC/HD gun, it shoots 165gr without a hiccup, and since picking up a 9mm OEM barrel I rarely shoot .40s&w much anymore.
I did have a M&P 40c that ate everything and asked for seconds so I figured the full size barrel must have been made on a Friday.