First, contstructive criticism:
I'm no AR expert but I can tell you that as difficult as it is to diagnose malfunctions via photographs, blurry photos make it almost impossible. Try laying the carrier key on a white background and make sure the image is crisp before you post it. Play with different lighting angles also to make sure you have good contrast on the critical parts. A shot of the gas tube might be useful as well since it's the seal between the two that gives sufficient energy to the bolt to get a full stroke.
By miss-feed do you mean that the round is not moving smoothly into the chamber or is the bolt failing to catch it at all leaving it in the magazine while the bolt closes on an empty chamber? If I recall my M-16 days correctly the bolt catch holds the bolt very near the rear of its travel. If it's not stripping a round at all and doing it frequently with multiple mags while not locking back it's apparent that the bolt is not moving to it's full rearward position.
If, as you say, everything is clean, lubed and moves freely without burrs then the problem is likely in the gas system. Clean the tube and make sure there is a good seal between the tube and carrier key. Obstructions or excessive leakage can both reduce energy transmitted to the bolt carrier and cause short strokes which would lead to a failure to eject, failure to lock back and cause the bolt to close on an empty chamber with rounds in the mag. It sounds like you may need a new gas tube and/or carrier key to get this thing running properly.
My opinion on the roles people play:
Firearms dealers are not necessarily experts in firearms, they are experts in sales and the administrative requirements to commercially sell firearms. Most firearms dealers are interested in firearms while other guys, like you'll find in the gunsmith forums, are interested not only in firearms but how they work; you came to the right place.
"How a politician stands on the Second Amendment tells you how he or she views you as an individual; as a trustworthy and productive citizen, or as part of an unruly crowd that needs to be lorded over, controlled, supervised, and taken care of."
- Dr. Suzanna Gratia Hupp, TX State Rep., GOP, Massacre Survivor
Last edited by Wenonah; 02-19-2011 at 08:44 PM.