Chambering problems...Hope somepne can help

[mlosi762]

Hey guys, took my first build to the range last week. Fired about 50 rounds of PMC 55gr .223, no problem. A buddy of mine came and brought some surplus m855 that he had. First round of that failed to chamber fully (bolt wouldn't go into battery, and FA did nothing to help), and we had to pry the BCG back with a piece of a cleaning rod (gouging up my ejection port in the process), to get the round out. Broke it down, inspected the chamber, cleaned it up, and tried again with a new round different pmag, same issue. This has happened now with several types of rounds not chambering. There's no obstructions lodged in there and I've tried everything I can think of, and nothing seems to work. Also, I'm well aware of the .223 vs 5.56 issues, but can’t even get a .223 to chamber now.

Barrel is a CMMG 1/7, 5.56 chambered, 16" carbine length.
BCG is Daniel Defense
BCM carbine length spring with H buffer.

Had an AR certified gunsmith check my installation work before I fired it (headspace/torque/etc), and he gave it a "go". Hope I can get some suggestions on what may be the problem before I have to spend $$$ on getting it checked out.

Could I have bought a crap barrel? Anyone else have issues with CMMG?

Thanks

[5pins]

The fact that you fired 50 rounds and did not have any problems until you tried some surplus ammo is too coincidental.
I would take a look at the barrel extension and make sure there is no obstruction.
Take a look at the bolt and make sure that the ejector and extractor are working properly. In fact just take the whole BGC apart and give it the once over.

[mlosi762]

The fact that you fired 50 rounds and did not have any problems until you tried some surplus ammo is too coincidental.
I would take a look at the barrel extension and make sure there is no obstruction.
Take a look at the bolt and make sure that the ejector and extractor are working properly. In fact just take the whole BGC apart and give it the once over.

That’s what I thought about the ammo too. But now nothing chambers at all. Already checked the barrel extension, nothing stuck in there, and cleaned the BCG real good when I first had problems. Pretty much gone over every user level PMCS procedure there is, and can't figure out the problem. I’ve had issued weapons get all kinds of crap stuck in the chamber and BCG while in the desert, but never seen malfunctions like this. It’s driving me nuts. I have a feeling I may have just got a shit barrel.

[Quib]

That’s a good troubleshooting problem you have on your hands.

It’s strange that up till the introduction of the M885, that the weapon functioned fine. How does the action feel with the weapon unloaded, just pulling back on and riding the charging handle slowly forward?

Can you feel a point along the bolt and carriers path, where you start to meet resistance?

[5pins]

If you have access to another AR I would try swopping BGC and see what happens.

Another thing you could try is to separate the upper from the lower pullout the BCG and try dropping a round in the chamber and see if it chambers.

[mlosi762]

That’s a good troubleshooting problem you have on your hands.

It’s strange that up till the introduction of the M885, that the weapon functioned fine. How does the action feel with the weapon unloaded, just pulling back on and riding the charging handle slowly forward?

Can you feel a point along the bolt and carriers path, where you start to meet resistance?

Going to play around a bit. Unloaded, then with some dummy rounds. Going to try using the BCG from my other upper to see if it chambers/cycles rounds. Hopefully I can narrow it down.

[mlosi762]

If you have access to another AR I would try swopping BGC and see what happens.

Another thing you could try is to separate the upper from the lower pullout the BCG and try dropping a round in the chamber and see if it chambers.

Lol. Just thought of that while repling to Quib. Thanks none the less though 5pins.

[mlosi762]

Going to screw around with this damn thing. If I can't figure it out, I'll take it completely apart and take some pics of the parts to see if anyone can spot something out of wack that I missed. Thanks guys.

[Quib]

Sounds good. Keep us updated.

[Optimus Prime]

I'd almost run a broken shell extractor through it just for the hell of it myself. I've seen a Ma Deuce with a busted case where the chamber looked fine, but sure enough, there was half a case lying under the gun, and it would not chamber a round. Just my 2 cents thrown into the mix.

[5pins]

I'd almost run a broken shell extractor through it just for the hell of it myself. I've seen a Ma Deuce with a busted case where the chamber looked fine, but sure enough, there was half a case lying under the gun, and it would not chamber a round. Just my 2 cents thrown into the mix.

I had the same thought.

[mlosi762]

So here's an update. Swapped out BCG's, same problem, so its not that. Has to be the chamber itself, right? So took the entire upper apart, and it looks like there may be a tiny bit of a case neck lodged in the chamber. Hard to see even with a surefire light pointed down in there. But will try and extract it (gotta go buy a shell extractor). If what I think I see isn't some brass, then I'm at a loss. Is it possible that this chamber just is't to spec? But if that's the case, I don't understand how I could run 50 rounds through it before having an issue. I have my 16" middy BCM BFH as my "main" upper, so I'm not having to go without, but will be pissed if I got to sink more money into my back up.

[5pins]

If it was out of spec I don’t see how you could have gotten 50 rounds off.

[mlosi762]

Likewise. Might just have to bite the bullet and take it to an armorer. But it's like changing the oil on my car, hate to pay someone else to do something I should be able to do myself. Hope it is just a piece of brass in there thats causing the problem. We'll see.

[rebelEMPIRE]

Sounds like that most likely is the case. If you can get your hand on a bore scope, it would help confirm things much more easily. Any possible debris must be jammed in there pretty tight, too. Good luck mate; I'm keeping an eye out on this thread.

-rebelEMPIRE