Originally Posted by txmadelatino
The bolt sometimes closes without chambering a round and also jams a round half way in the chamber and half way in the mag with the extractor pinning it against the side. Then it doesn't lock back after emptying a magazine. I took the carrier key off the carrier and cleaned all well i just need the tools to replace it and give it the correct seal needed.
Remember not to place too much by my advice, I'm just working from a general troubleshooting standpoint, I am not
an AR expert.
Both of those issues can be from the bolt not moving completely to the rear. With the bolt getting just far enough back to grab the round it can't overcome the friction from the mag lips. With most autos the bolt moves about 3/8" or more past the rear of the mag. This lets it get a little inertia going to overcome magazine tension and strip the round. Does it ever fail to load when you pull the charging handle all the way back and release it? If it always loads reliably when manually charging then it's pretty well down to the gas system and a full strip down is in order. If it sometimes jams when manually charging it could be varnish or a dirty recoil spring/plunger. You will never regret getting that varnish out though.
On the photos, the critical part of the gas tube is the end where it mates with the key, that is your most likely point for a leak. I don't know if you can get a picture of that without removing the barrel, gas block or both. It's starting to sound like you're going to have to see the gunsmith if removing varnish or cleaning the recoil spring don't fix you.
Don't forget to get that key re-peened. You don't want that working loose.