Gary, I'm having the same problem on a new M&P 15 Sport II. I've read on two different forums how sending it in to customer service did not resolve the problem. How did your rifle shoot after those 30 rounds?Well guys I think I have found/fixed the problem. I separated the lower from upper and when checking out the parts in the area of the trigger, hammer and disconnector I found that a primer had blown off a casing and what was left of the primer was under the mechanism the disconnector sits in and was keeping the disconnector from doing it’s job. In other words the primer was keeping it form moving down as it should to release the hammer properly. How wild is that? Ever hear of a primer coming out of the casing? And it was Lake City ammo, not junk.
I have my fingers crossed that the situation is under control. I shot another 30 rounds and it was working fine.
I learned a lot about AR trigger assemblies in the course of al this. Thanks for the advise.
After reading the experiences of others and inspecting my feed ramps, I found that the transition from the receiver to the barrel is not smooth or even...the barrel feed ramp is noticeably higher such that if you run the tip of a pen up the feed ramp, it will get caught on the leading edge of the barrel. This does not happen with a different upper that I tested. Here is what happened to about a dozen of my rounds:Gary, I'm having the same problem on a new M&P 15 Sport II. I've read on two different forums how sending it in to customer service did not resolve the problem. How did your rifle shoot after those 30 rounds?