What Rob1 said......
and the obligatory (YAWN) here goes...make sure you are stagger loading the mags correctly...numerous thread on this.
If the problem persists your ejector could need bending....numerous threads on this.
If the problem persists you may need to invest in the VQ extractor...numerous threads on this (note to S&W - i have run the factory extractor for 1000's of rounds, never had one FTE or stovepipe)
If the problem persists...send the rifle back to S&W and they will repair under warranty.
If the problem persists.....well you didn't try and remove the flashhider by clamping the upper and not the barrel...did you know you can twist the barrel in the upper by doing that.
I can run my rifle for 1000's of rounds before i 'clean' it - no issues....it gets cleaned after each range trip because i enjoy the process.