Finally solved
I took the weapon to another Smith & Wesson gun smith at another lgs. They test fired it and had the same problems. The buffer spring, gas system all checked out ok. The problem was in the extractor in the bolt. S&W had installed at the factory a plastic piece in the extractor...
Thank you all for the posts. I did clean it thouroughly between the 1st and 2nd trip to the range.
I will contact S&W. I just hate to give up a weapon that I waited so long to get.
Purchased the gun on May 29th 2014.
I took it ot the range and every other shot was a misfire. I would drop the mag (Magpul) and recytle the bolt and the gun would fire. I would reinsert the mag and cycle the bolt and the next shot would be fine but I would get a misfire again. This continued...