AR 10 extraction problem

[homesick]

I'm kinda new at the AR thing so I need your experience please.
I have a PSA AR 10 which worked fine but it had a Magpul full stock on it. How ever it was very heavy so I had an adjustable stock installed. Today when I shot it would not extract the empty let me rephrase that, it tore the lip off the brass. Brass was stuck in chamber.
Like I said it worked fine earlier

 

[Mobuck]

Was the proper buffer and spring replaced in the tube? If it worked fine prior to the change, then the cause must be related to the new parts.

 

[homesick]

Because the new stock was a different design the old buffer and spring weren't used. I can only guess this is where the problem is.

 

[stagpanther]

The buffer and spring are different in a carbine extension tube. That may be a factor in your jammed case--but it sounds to me you may have had a bad head-spacing of your cartridge. What kind of ammo was fired?

 

[Mobuck]

"The buffer and spring are different in a carbine extension tube. That may be a factor in your jammed case--but it sounds to me you may have had a bad head-spacing of your cartridge. What kind of ammo was fired?"

So, how would changing the buffer tube/stock affect the headspace?
OP says "I have a PSA AR 10 which worked fine but it had a Magpul full stock on it."
Tearing the rim off is a whole different symptom vs head space issue. Sounds more like little/no resistance to primary bolt cycling/extraction. I vote for incorrect buffer/spring combination OR assembly.

 

[stagpanther]

"The buffer and spring are different in a carbine extension tube. That may be a factor in your jammed case--but it sounds to me you may have had a bad head-spacing of your cartridge. What kind of ammo was fired?"

So, how would changing the buffer tube/stock affect the headspace?
OP says "I have a PSA AR 10 which worked fine but it had a Magpul full stock on it."
Tearing the rim off is a whole different symptom vs head space issue. Sounds more like little/no resistance to primary bolt cycling/extraction. I vote for incorrect buffer/spring combination OR assembly.

In all my years of doing virtual Internet analysis, one thing I've learned--it's very hard for me personally to make a diagnosis (aka semi-informed guess) without having the weapon and evidence in hand--I make no claims as being an expert and therefor correctness of my guesses. ; )

However--the key piece that leads me to suspect a headspace problem--whatever the cause might be--is the case jammed in the chamber and the fact that the trigger still was able to fire a cartridge that was enough into battery. Wasn't clear whether the rim was torn on insertion or extraction either. Seems unlikely that a bolt would completely tear off a rim simply from the cycled gas from the gas tube--so yeah--perhaps something was weird with the way the BCG was operating. Either way I wouldn't fire the thing again until I was sure everything was in spec.

 

[Theohazard]

I'll bet that Mobuck is right: The problem is that the OP switched to a buffer and/or spring that's too light. I'll bet just switching the buffer to a heavier one will fix the problem; many rifles and buffer system kits come with lightweight buffers because they're cheaper and they usually work OK. But if the extractor is tearing the case rim and leaving the case in the chamber, that's a classic case of overgassing: The BCG is going to the rear too quickly and trying to extract the case when the gas pressure is still too high and the case is still expanded and sealed to the chamber wall.

The root of the problem is too much gas, so another option is to play around with an adjustable gas system. But the simplest solution is to switch to a heavier buffer.

 

[stagpanther]

I'll bet that Mobuck is right: The problem is that the OP switched to a buffer and/or spring that's too light. I'll bet just switching the buffer to a heavier one will fix the problem; many rifles and buffer system kits come with lightweight buffers because they're cheaper and they usually work OK. But if the extractor is tearing the case rim and leaving the case in the chamber, that's a classic case of overgassing: The BCG is going to the rear too quickly and trying to extract the case when the gas pressure is still too high and the case is still expanded and sealed to the chamber wall.

The root of the problem is too much gas, so another option is to play around with an adjustable gas system. But the simplest solution is to switch to a heavier buffer.

I agree that the use of the wrong spring and buffer--if that's in fact what happened--could contribute to the problems especially if the carrier timing is off--and I think you are definitely on to something with the gas pressure likely being too high. It's hard to tell what the OP meant by stuck case--it could simply be sealed to the chamber and hard to get out due to the extractor not having enough rim to grab--or it could in fact be over-pressured due to faulty chambering of the cartridge on load and firing. My point is--rather than get into an argument over what it may or may not be--I'd simply check and eliminate all possibilities. If the OP puts a rod in the bore and the spent case pops out without too much resistance--then yeah--probably had a normal ignition--if it doesn't, and the case is expanded beyond normal measurements--especially in the head web area--that would send a red flag up for me to be concerned about more than just the right buffer and spring. But I could be totally wrong in my guesses. ; )

 

[Theohazard]

Stagpanther, I don't think your line of thinking is flawed at all. But the fact that the OP previously had a full-length rifle buffer tube with the heavier rifle buffer and it worked fine is a pretty strong clue. His rifle worked fine, then he switched to a carbine buffer system that almost certainly came with a lightweight carbine buffer (because almost all carbine buffer kits do) and his rifle is now exhibiting the classic signs of having a buffer that's too light.

You're right that we can't know for certain, but this is one of the more obvious online diagnosis threads I've seen. Sure, Mobuck and I could be wrong, but I'd be willing to bet that a heavier buffer will fix the problem.

 

[stagpanther]

Stagpanther, I don't think your line of thinking is flawed at all. But the fact that the OP previously had a full-length rifle buffer tube with the heavier rifle buffer and it worked fine is a pretty strong clue. His rifle worked fine, then he switched to a carbine buffer system that almost certainly came with a lightweight carbine buffer (because almost all carbine buffer kits do) and his rifle is now exhibiting the classic signs of having a buffer that's too light.

You're right that we can't know for certain, but this is one of the more obvious online diagnosis threads I've seen. Sure, Mobuck and I could be wrong, but I'd be willing to bet that a heavier buffer will fix the problem.
__________________
0331: "Accuracy by volume."

And I don't think you guys are wrong either--but if he installed the correct buffer and spring for the carbine extension--and as you observed the system is possibly over-gassed--I would be looking at solving the problem with adjusting the gas rather than masking the issue with heavier spring/buffer. The OP still hasn't said anything about using the wrong buffer/spring etc. In fact--he hasn't said much of anything. : )

PS--Now that I think about it--I'm wondering--"what are the odds that the OP bought the PA10 buffer and spring combo from PSA" which in fact are really designed as heavy AR15 components or "shorty" carbine extensions--I made the same mistake initially buying this for my recent creedmoor build??

 

[Quentin2]

Besides the buffer and spring, the carbine receiver extension/buffer tube should be longer to allow for the longer 308 AR bolt carrier which can bottom out in a regular 5.56 tube. I know a real AR-10 (ArmaLite) carbine tube is 3/4" longer - then a standard H3 heavy carbine buffer is used. Not sure how PSA sets up the PA10 but you want to do it their way.

 

[madcratebuilder]

Besides the buffer and spring, the carbine receiver extension/buffer tube should be longer to allow for the longer 308 AR bolt carrier which can bottom out in a regular 5.56 tube. I know a real AR-10 (ArmaLite) carbine tube is 3/4" longer - then a standard H3 heavy carbine buffer is used. Not sure how PSA sets up the PA10 but you want to do it their way.

This! If the OP used a 5.56 AR RE, buffer and spring that's the first thing I would look at. There is a sticky at arfcom that covers the different RE's and buffers used with .308 AR's.

 

[stagpanther]

edit

 

[gman3]

My PA 10 which came from them with the adjustable stock and carbine length buffer tube functioned okay, but was absolutely destructive on brass. The more robust Lake City brass fared pretty well, but other stuff like Federal brass which is softer, received gouges in the case head, deformed extractor grooves etc. Had all sorts of problems with Hornady brass. I also think that it needs a heavier buffer.

The weapon was WAYYY overgassed. An adjustable gas blocked cured that. It also had a dent in the crown, and the barrel was hand tight. Pays to go over their stuff and check things out. As Forest says "you never know what you're gonna get"