When I fire my AR, the bolt/carrier will attempt to feed another round into the chamber, the only problem is, the spent shell casing is still in the upper receiver. It is usually lodged on top of the live round facing forward towards the chamber. It appears that the rifle is attempting to charge both the live round and the spent casing.
Thanks,
Russell

Sounds like your Extractor....check it...clean it...just a thought...

are you using Olympic SS109? I had the same problem. I switched to S&B and it worked fine

Sounds to me like it's "short stroking". This is sometimes caused by shorty barrels or gas leaks on regular barrels, case being neither has enough gas to fully retract the bc back enough to eject & feed properly.

First thing is change ammo. Second is make sure everything is lubed properly. Make sure the gas tube is pinned & it has no kinks in it.

Hope this helps.

This seems to be the most common problem experienced by AR owners. It is almost certainly a result of a weak extractor spring.  Yes, it does look like short recoilling, but 99% of the time it isn't.

Solution? Get a couple of extractor springs from Wolff Gunsprings  www.gunsprings.com and it will almost certainly solve the problem.  Be sure and use the little blue buffer piece that sits inside the spring.  Don't worry about any note that says to use a black insert. It's exactly the same as the blue one.

Thanks for all the help! I'll order new springs today.
Russell

I had a very similar problem with my M4gery recently.  Spent cases stovepiping, or just staying in the receiver while it's trying to feed the next one.  I immediately though "extractor," so I clean everything real well, paying close attection to the extractor.  Seemed to fix it, for about 5 rounds.  I replace the extractor.  Same thing.  Check the ejector.  Same thing.  Changed ammo.  Same thing.

I finally figured out that it was short stroking, then looked at the gas system.  The carrier key had worked itself loose, just enough so that right after I clean, the clp I threw in there for lubrication would seal it, but after a few shots, the clpwould burn off and gas would start leaking out, causing it to short-stroke.  Tightened and re-staked the key on, and haven't had a problem since.