I recently took my college age grandson to the range he is in love with grandma’s Henry H01. While he emptied and reloaded it twice, I did the same with my AR-15, which he had never fired. So, I put a new magazine in the AR-15 and handed it to home. He put the first round in the target at 100 yards. I didn’t see a casing eject and at first i thought I just blinked and missed it. He pulled the trigger a second time and it wouldn’t move.
It took back the AR-15 and the charging handle would not move back, The bolt carrier was slightly back from the firing position, but none of the extractor was visible. The forward assist does nothing. The Safety Selector Lever moves a little bit but not all the way to the Safe position. The Takedown Pin works, but nothing else does.
If you have to and you are sure you have an empty casing stuck in the chamber run a cleaning rod down the barrel and into the casing and taping on the rod with a hammer may work. Good luck.
New AR? Did you clean it before you fired it? Did you break it down and clen all the parts? Clean the barrel? Did you put gun oil on the parts and check the operation before you put any rounds in it? Did you run a cleaning brush through the barrel after firing it the first time?
I hear that referred to as “mortoring”. Doing that while pulling back on the charging handle can unstick a fair bit of things. Just watch that muzzle direction of course. Running the stock into a table top or similar can help keep the muzzle above you
I’ve even seen people use their feet on a charging handle (different rifle types) while doing this. Best done to your own gun in case you break it hehe
Mortar it to unstick it then pull it apart and check everything. Check the barrel for a squib load! I’d clean it and try it again if it were me. You can look up videos on how to mortar one if you’re unsure. It’s easy and won’t hurt it.
once you get it cleared check the chamber for burrs or rough spots from machining… I purchased a new 300 blackout upper that had the same issue
it was leaving gouge marks on the brass.
it also was not chambering properly
till I cleaned it up
If I read your post correctly, you had already run two mags worth of ammo through your AR. Then it jammed. With a semi-auto I always inspect the rounds before inserting them in the mag. While ammo is amazingly uniform, it is always possible for something to happen when you are making ten thousand of something an hour. It never hurts to clean and lube a firearm after use although I had a professional shooter tell me he never cleaned his firearm, just lubed it on the parts that need it. Different strokes. While I am posting, this is directed at the folks who run this site. I am getting just a little tired of the pop up ad for whatever it is you are hawking. I just may quit this site because of the frequency with which it appears. Be advised. With the M-1 when it jammed like that we used to kick the operating rod handle to clear it. Don’t know if an AR could stand that but you might try tapping the operating rod handle with a rubber mallet. I wouldn’t hammer on it with a metal hammer. I don’t think a cleaning rod down the muzzle will clear your problem but I have been wrong a time or two in the past.
I had same thing happen to my AR when I put out of spec ammunition.
Here is how I knocked the BCG loose.
Take the rifle apart, set the upper upside down, take a screw driver and put it against the BCG edge with a cloth (Not towards the firing pin) take a mallet, and it should free it up.
Thanks to everyone for their suggestions! This is a really great community!
I decided to try and “mortar the AR-15” first. But before I did that I did a search on YouTube and watched this https://www.youtube.com/watch?v=vbDPNbg2QpM&t=13s and one other similar one that used a table. Since I didn’t have a 55 gallon drum or a table I didn’t mind banging on, I decided to sit on the concrete floor of my back porch. One of the videos said it might take multiple attempts to work. True. The brass ejected on my 3rd try.
I then proceeded to break it down for cleaning. The Ejector Pin came out in two pieces.
Everything else looked normal, so I am sure that was the problem. I had a spare ejector pin, so it is now repaired and manually cycles brass normally, so it is ready to go back to the range.
Fixed. See post below with picture for details. 
