More extraction issues

[nocoolname]

First the gun details:
20" BHW bull barrel with rifle length gas system, Type 1 chamber
BTE adjustable gas block(double checked to make sure it's aligned properly)
Underground tactical 7.62 bolt in a 2 vet arms NiB BCG
Carbine buffer tube, spring and buffer.

Now onto the problem. I've had some extraction problems that developed after round 73, where it just stopped extracting. I inspected everything and tried the o-ring fix, which worked for one range trip where I shot about 35 rounds and then it started to fail to extract again. Today I decided to play with the gas system and could still not get an extraction. I turned the gas down so much that an empty magazine would not lock the magazine back all the way to adjusting the gas block wide open with no changes. The only thing I have left to do is change buffer weights, but I'm not certain that would fix my problem and am debating trying a different bolt.

Some other things, there is no markings on the case that looks like the extractor is slipping off the rim, and if I drop the bolt on the non extracted but fired round and then pull it back, it will extract just fine.

[LRRPF52]

Check the chamber for burrs or rough tool marks.

Is the extractor bent by any chance?

What ammo?

[nocoolname]

Check the chamber for burrs or rough tool marks.

Is the extractor bent by any chance?

What ammo?

I checked the chamber the best I could with a flashlight and my naked eye. I don't have a boroscope, but this gives me a good reason to pick one up. I'm also not seeing any markings or gouges on the case to indicate anything in the chamber.

If it is bent, I can't tell that it is, but I'll check with a straight edge to make sure.

Hornady 123 A-max factory loads and my reloads, which I am running the max of 31gr of CFE in Hornady brass with 123 A-max bullets.

[204 AR]

Is it jumping over the rim and leaving the case in the chamber, or is it just not pulling back far enough to bring it out of the chamber and eject? Could your gas key have come loose?

[LRRPF52]

Gas key was the next question I was going to ask. A good indicator of a loose key is carbon leaking from the key to carrier joint, but they will wiggle a tiny bit even when they start to get loose on a carrier that wasn't assembled securely, or tampered with.

Next after that is carrier key clipping the gas tube. Check your gas tube flange to make sure one side isn't worn down from clipping.

[nocoolname]

Is it jumping over the rim and leaving the case in the chamber, or is it just not pulling back far enough to bring it out of the chamber and eject? Could your gas key have come loose?

It's jumping over the rim and leaving the case in the chamber. Since I was playing with the gas and trying to diagnose it today I only had one round at a time in the magazine. When the bolt would lock back on the bolt catch, I could see the case was still fully in the chamber. I've inspected the cases and the case head doesn't show any marks of the extractor trying to rip the case apart either.

Gas key was the next question I was going to ask. A good indicator of a loose key is carbon leaking from the key to carrier joint, but they will wiggle a tiny bit even when they start to get loose on a carrier that wasn't assembled securely, or tampered with.

Next after that is carrier key clipping the gas tube. Check your gas tube flange to make sure one side isn't worn down from clipping.

Thanks for the pics and the info from both of you guys. I'll disassemble the rifle tomorrow, check everything reccommended and take pictures of the cases from today as well as anything else that looks suspicious or suspect to get your guys opinion on.

[LRRPF52]

Carbine buffer. I just noticed that. You need an H2 at least. Your bolt is unlocking too early, while the case is still obturated in the chamber under pressure. The reduced combined mass of the BCG and carbine buffer doesn't provide the resistance needed, so the gas expansion cycles the carrier faster.

[nocoolname]

Sorry to be so long on getting back to this, but I installed a Spike's T2 buffer, (same weight as H2 buffer) and it didn't change anything. Bolt comes back, locks against the bolt release and the spent cartridge is sitting in the chamber.

I can't find any marks on the brass that indicate a burr in the chamber, can't see anything in the chamber that would indicate it, double checked my bolt, BCG, the gas tube for odd wear and can't find anything that would point to even a possible problem unless I'm greatly overlooking something. I'm about to just send the upper off for someone to troubleshoot, but don't know where I could send it.

[terrywick4]

have you tried to put a case in the bolt outside the chamber?

[SG4247]

Sounds like a broken (chipped) extractor claw...

Been there done that.

Post a photo of the extractor claw and we will know right away if that is the culprit, or if the chamber is rough.

[LRRPF52]

Will it manually extract a cartridge from the chamber?

[Wheelhorse]

Sounds like a broken (chipped) extractor claw...

Been there done that.

Post a photo of the extractor claw and we will know right away if that is the culprit, or if the chamber is rough.

Yep, that carbine buffer made life extremely hard on the extractor until it gave way.
You're right about the photos that would help a lot, but I think you're barking up the right tree.

[nocoolname]

have you tried to put a case in the bolt outside the chamber?

Yeah, it fits and you can tell the extractor claw is grabbing the rim. Feels very similar to my .223 ARs.

Will it manually extract a cartridge from the chamber?

Yeah, it extracts the round fine if I cycle the bolt by hand. I did notice that if I run it with the gas off that it's hard to pull the charging handle back after firing, but if I have the gas adjusted to where the BCG fully cycles, that I can manually cycle the bolt and it will extract easily.

Sounds like a broken (chipped) extractor claw...

Been there done that.

Post a photo of the extractor claw and we will know right away if that is the culprit, or if the chamber is rough.

Here's a few pics of the extractor by itself and while still in the bolt. I can't tell of any deformities of it.

[LRRPF52]

Pics of spent cases is what I need to see next.

[SG4247]

While not broken, I do have a couple of concerns with this extractor.

I will post a couple of pics here shortly.