I have a bushmaster ar15 (.223) that I got probably 10 years ago. Never changed anything out and I’ve shot thousands of rounds through it. I haven’t had a problem whatsoever until recently. It’s been double feeding quite a bit so I got new pmags and didn’t fix it. Then I gave it a very good cleaning and it seemed like it got somewhat better but not how it should be. I also noticed that when I rapid fire it does not jam.
Everything in the bcg seems fine. I’ve been shooting 55 grain PMC ammo.

Anyone have any guesses? I was thinking it might be the gas block or maybe I just need a whole new bcg since everything is years old with thousands of rounds shot through it. It’s been an absolute great rifle though. Let me know what you guys think, thanks.

Is the fired casing still fully in the chamber when it trys to feed a new round?  

I would give it a good cleaning to include the chamber with a chamber brush.

Yeah, it’s always still in the chamber and then tries feeding a new round in and then it gets a little dented from the bolt pushing it forward and having no where to go.
I’ll clean the chamber really good and see if that helps. Last time I cleaned it (a month ago) and shot it, it was definitely better but still doing it 25% of the time. Property has been wet so haven’t been able to shoot for a few weeks. I appreciate the response, I’ll try that out.

Springs. Extractor and ejector springs are probably tired as hell. Install some new ones and see what happens.

You’re not having a double feed.  That’s a failure to extract.

Change the bolt.

I mix those up lol. But sounds good, which one should I go with? I’ve seen a lot of people recommend BCM, DD, and Toolcraft. Does it really matter? Wasn’t really trying to spend over $200 for a bcg.

Just replace the bolt. DD, BCM, SOLGW, Colt, all good.

You could probably just replace the extractor, spring, and insert and be fine too.

Sounds good, I appreciate the response.

I Appreciate it.