Smithwessonshooter,

Best thing you can do at this point is send it back to Smith and Wesson Its brand new and under warranty, so save yourself a
lot of aggravation. Of course, its your rifle, and you can do what you want.

My point is why throw parts at it and try to fix it at your expense?
Clearly something isn't right with it. Based on what you're saying,
you've done all the right things. Clearly, the problem is in the rifle.

Now I have a MP15 Sport 11. After 1500 rounds, it started to
short stroke. Jamming, not picking up fresh rounds, etc. The
bolt wasn't being blown back far enough to pick up the next fresh round. Happened with any magazine, and any factory ammo I used (PMC, Federal, Winchester.) Problem is definitely
in the gas system.

I could throw a new bolt in it, or new gas rings, but why should I pay for a new $80.00 (roughly) bolt while its under warranty?
S&W sent a ticket to get it returned, and that's where its at right now. Your rifle, your choice. If you check out all the
things which might cause your problems, and cant resolve it, a trip to S&W might be in your best interests.