My ARs jam more than Smuckers. I clear it by grasping the charging handle and stroking the butt against the ground smartly while pulling down on the handle. The inertia will pretty much clear any jam. I've had spent cases get lodged between the bolt key and the raceway under the carrying handle. That's a tough one to get out. It requires that you get in there with a small screwdriver and just poke around until it comes out.
I assume you have the magazine out. I have found that those green followers will jam the carrier when you pull it back and there are no rounds in the magazine. Those green ones are junk anyway. Get the Magpul replacements-- they work 1000%. I just two days ago put a Defender d-ring into my varmint AR and a little o-ring into my carbine because I was having half-extraction problems. These things cost over $12 apiece. Go to your hardware store and buy the teeniest, tiniest little o-ring you can and slip it over your extractor spring. This will increase the clamping force of your extractor on the rim by several hundred percent. The one I paid so dearly for was about 1/4" in outside diameter, had a hole in it about 1/10" in diameter and was about .068 to .075 inches thick. Now that I know I can go and buy this ring for nine cents, I pass the info on to others.
I assume your upper has a forward assist on it. Take a rubber mallet and bump the carrier forward. Once you have the upper open, look inside for grit or an excess of unburned powder that could be locking you up.
If you are totally stuck you might try taking the buttstock off, then removing the buffer tube. Watch for springs and other stuff to come flying out and off the gun. Do all of this slowly. Watch for the small detent spring for the safety to get lost when the buttstock comes off. It's directly aft of the safety on the right side of the gun, in a small hole drilled into the lower. Don't bend it when you put the stock back on. All it takes to get the stock off is an allen key. Remove only the top screw. Removing the buffer tube may take a strap wrench or a big set of hands with a good, tight grip. When you take the tube off, watch for the plunger retainer detent at the forward end of the tube/rear of the receiver. The buffer tube holds it in. Taking an AR apart is not that hard to do. Just be slow and deliberate, watch from where things came and don't rush or force it back together.