OldTurtle
Moderator - Deceased
One more item to check, since I ran into the same problem with a relatively new AR. Pull your action spring and buffer and make sure they are clean and lightly lubed. By light, I mean that after lubing, wipe off the excess and when you run your finger over the surface, you should not be picking up excess on your finger.
A second item is to make sure your chamber is really clean as new chambers seem to accumulate crud much easier than those that have be shot for a while. I had a gunsmith recommend chucking a piece of cleaning rod into a cordless drill and using the chamber brush, place some oil on the brush and operating it at slow speed in the chamber for a few seconds... I've never had a problem since.
A second item is to make sure your chamber is really clean as new chambers seem to accumulate crud much easier than those that have be shot for a while. I had a gunsmith recommend chucking a piece of cleaning rod into a cordless drill and using the chamber brush, place some oil on the brush and operating it at slow speed in the chamber for a few seconds... I've never had a problem since.