Do AR gas rings wear?

[Varminterror]

The common gas ring condition test is to extend the BCG outside of the rifle and stand it on its nose. If the carrier collapses on the bolt, replace the rings, if not, it’s groovy.

Confirming, it is absolute urban legend, unfounded, that aligning the splits of the 3 rings will cause issues. If a rifle isn’t running properly because of aligned slits in gas rings, the rifle isn’t running well at all, for some other SIGNIFICANT reason.

 

[nipprdog]

If you haven’t tested the bolt as described in post #2 then you’re simply wasting time and looking to throw money at it. Test it. Period.

Yep

 

[wesmonster]

I agree with trying the bolt test, easiest way to check rings. Coatings shouldn't matter. I have several nitride and a NiB bcg that can both pass this test, as well as my phosphate bcgs.
I also agree replacing a few springs is the simplest & cheapest solution. Now at 5k if you don't have a spare bolt, get one. But sounds like OP is stating this started all of a sudden.
And as mentioned earlier, if it locks open on last round, it's cycling properly and not a gassing problem.

 

[Charlie98]

I agree with trying the bolt test, easiest way to check rings. Coatings shouldn't matter. I have several nitride and a NiB bcg that can both pass this test, as well as my phosphate bcgs.
I also agree replacing a few springs is the simplest & cheapest solution. Now at 5k if you don't have a spare bolt, get one. But sounds like OP is stating this started all of a sudden.
And as mentioned earlier, if it locks open on last round, it's cycling properly and not a gassing problem.

As an update...

Yes, I have a backup BCG, but I didn't have it with me when I was shooting in NV... because the best place for spare parts is on the shelf back in Texas...

I did pull the bolt apart, again, yesterday, and compared it to the brand new bolts I had handy, including the BCM spare. The extractor seems fine... I was not really having problems with extraction, nor with the bolt locking back on empty. Using a case set in the bolt, I compared spring tension of the ejector... and that might very well be the problem, it certainly did not provide the tension the others did. Thinking back on the instances of stovepipes... the bolt obviously fully cycled... there was a live round in the chamber each time with the stovepipe, so it cycled, it's just that the empty never got out of the way.

In the meantime, I swapped in the BCM bolt into my chrome carrier, and I'll take it out this week to see. I've got a list of spare parts I need to order, including extractor claws and cam pins, then I'll rebuild the old bolt and see if I can fix the problem.

 

[lysanderxiii]

The field test for military BCG is to extend the bolt and stand the the BCG on it. If the carrier slides on top of the bolt under its own weight, it's time to change the rings.

The common gas ring condition test is to extend the BCG outside of the rifle and stand it on its nose. If the carrier collapses on the bolt, replace the rings, if not, it’s groovy.

You all have it backwards. The rings only have to hole the weight of the bolt, not the bolt carrier.

TM 9-1005-319-23&P, WP 0011:

 

[bubbatime]

5000 rounds is time for some new springs. I’d replace all of them, to include the buffer spring and trigger pack springs.

If it were my rifle the bolt and can pin would get replaced and the old bolt rebuilt with new extractor, extractor spring, and ejector spring and kept as a spare.

 

[Varminterror]

In fairness, I do expect most rings will resist far, far more than the weight of the carrier OR the bolt. These are all retracted, some with tens of thousands of rounds fired, and are holding at least the amount of weight pictured.

 

[Charlie98]

Did You change powder or loads anything like that ?

This is with factory LC.

So I think you mentioned something about taking it completely apart and cleaning the heck out of it and putting it back together? Have you shot it since doing so?

The short version timeline on it...

Ran fine for about 5000 rounds... 100%. At Christmas, it started to stovepipe once in a while... I put it down to out of spec LC ammos. I changed to PMC, and still had the occasional jam.

Brought it back to TX and broke it down. Cleaned everything, checked everything... nothing amiss, so I put it back together and ran some ammo... occasional stovepipe.

Broke it down again, pulled the gas block and tube. Swapped the bolt, which appeared to have a weak ejector spring, with a NEW BCM bolt, same carrier. Reassembled... headed to the range. Stovepipes/over round jams... but the only thing different was I was using a brass catcher (I was indoors and didn't want to lose my brass.) I've never previously had an issue with the brass catcher, so I believe it's a continuation of the ejection issue.

The bolt is fully cycling... because there is always a new round headed into the chamber, or in the chamber. The bolt locks back on an empty mag. I run my AR's wet... so, plenty of lube.

 

[Charlie98]

Just and example of what I'm seeing...

 

[45/30-06OKIE]

This is with factory LC.



The short version timeline on it...

Ran fine for about 5000 rounds... 100%. At Christmas, it started to stovepipe once in a while... I put it down to out of spec LC ammos. I changed to PMC, and still had the occasional jam.

Brought it back to TX and broke it down. Cleaned everything, checked everything... nothing amiss, so I put it back together and ran some ammo... occasional stovepipe.

Broke it down again, pulled the gas block and tube. Swapped the bolt, which appeared to have a weak ejector spring, with a NEW BCM bolt, same carrier. Reassembled... headed to the range. Stovepipes/over round jams... but the only thing different was I was using a brass catcher (I was indoors and didn't want to lose my brass.) I've never previously had an issue with the brass catcher, so I believe it's a continuation of the ejection issue.

The bolt is fully cycling... because there is always a new round headed into the chamber, or in the chamber. The bolt locks back on an empty mag. I run my AR's wet... so, plenty of lube.

So this rifle is not ejecting properly? What caliber is this rifle? Seems like it could be a weak ejector spring, maybe a new double ejector bolt is needed? I know people online say that they get better reliability out of a double ejector on 308 ARs but mine has a standard bolt and runs great!

 

[45/30-06OKIE]

Just and example of what I'm seeing...

View attachment 1142153

View attachment 1142154

Holy cow! I would get a new gas tube and try that!!! That's EXACTLY WHAT my 308 was doing!!

 

[Charlie98]

So this rifle is not ejecting properly? What caliber is this rifle? Seems like it could be a weak ejector spring, maybe a new double ejector bolt is needed? I know people online say that they get better reliability out of a double ejector on 308 ARs but mine has a standard bolt and runs great!

It's a 5.56mm. Remember... I found the ejector spring to be a little weak, so I swapped the entire bolt with a brand new BCM bolt... the ejector spring is not the issue, or not the sole issue.

I've built 2 AR-10's... one in .308, one in 6.5 ManBun. The -15 and the -10 are 2 completely different animals, regardless of their similarities. The -10 can require some amount of tuning, sometimes, to get them to run right. -15 not so much.

Looking back, the gas tube only has about 3000 rounds on it. As delivered from RRA, it had an overheight gas block on it... so I had to swap out the whole gas block and tube assembly early on. Come to think of it, the chrome bolt and carrier are not original, either.... but it has worked 100% up until now.

I want to sleuth this out, however... this is the first real problem I've had with ANY AR (besides my issue pieces...) so I'mma work through the problem so I have a definite answer.

 

[powermad]

It sounds like it's got plenty of gas as it is locking back on the last round.

The cyclic speed may be a factor.
The BCG could be out running the spent case.

A gas port that was on the larger size may be a bit larger now with 5,000 rounds.
A weak action spring with a 3.5oz buffer and bigger than necessary gas port can give you grief.

 

[45/30-06OKIE]

It's a 5.56mm. Remember... I found the ejector spring to be a little weak, so I swapped the entire bolt with a brand new BCM bolt... the ejector spring is not the issue, or not the sole issue.

I've built 2 AR-10's... one in .308, one in 6.5 ManBun. The -15 and the -10 are 2 completely different animals, regardless of their similarities. The -10 can require some amount of tuning, sometimes, to get them to run right. -15 not so much.

Looking back, the gas tube only has about 3000 rounds on it. As delivered from RRA, it had an overheight gas block on it... so I had to swap out the whole gas block and tube assembly early on. Come to think of it, the chrome bolt and carrier are not original, either.... but it has worked 100% up until now.

I want to sleuth this out, however... this is the first real problem I've had with ANY AR (besides my issue pieces...) so I'mma work through the problem so I have a definite answer.

Hmm ok do you have any known good springs and buffers? Cause you might try a new standard spring and buffer and test that as a base line?

 

[Charlie98]

It sounds like it's got plenty of gas as it is locking back on the last round.

The cyclic speed may be a factor.
The BCG could be out running the spent case.

A gas port that was on the larger size may be a bit larger now with 5,000 rounds.
A weak action spring with a 3.5oz buffer and bigger than necessary gas port can give you grief.

I'm kind of thinking that's the root of the problem. I've never dinked with buffer weight... I've never had to... but setting here after the last range session, trying to cypher it out... that's my next move.

 

[Charlie98]

Hmm ok do you have any known good springs and buffers? Cause you might try a new standard spring and buffer and test that as a base line?

I've got a brand new AR I just built.... I think I'll swap them out and see.

 

[Charlie98]

As a follow up to this thread...

As I mentioned previously, I swapped the chrome bolt out for a brand new phosphate BCM bolt. During a 120 round test fire, I had several jams... but I was shooting with a brass catcher, so I don't know if that was a factor. The BCG is still fully cycling, because it always locks back on empty, and when it jams, it's with a fresh cartridge.

I ordered a new spring (Sprinco white) and H1 buffer. If I have time this week I'll give it another test drive.

I did disassemble the chrome bolt... as I mentioned previously,I thought ejector tension was a little light...



...original spring on top, new spring on the bottom.


As an aside... a few months ago I spent a fair amount of money on an AR assembly block, and some vice blocks. They are absolutely worth the money, not only making maintenance easier, but with FAR better results. It's one of those 'now, why didn't I do this sooner' moments....

 

[45/30-06OKIE]

As a follow up to this thread...

As I mentioned previously, I swapped the chrome bolt out for a brand new phosphate BCM bolt. During a 120 round test fire, I had several jams... but I was shooting with a brass catcher, so I don't know if that was a factor. The BCG is still fully cycling, because it always locks back on empty, and when it jams, it's with a fresh cartridge.

I ordered a new spring (Sprinco white) and H1 buffer. If I have time this week I'll give it another test drive.

I did disassemble the chrome bolt... as I mentioned previously,I thought ejector tension was a little light...

View attachment 1143944

...original spring on top, new spring on the bottom.


As an aside... a few months ago I spent a fair amount of money on an AR assembly block, and some vice blocks. They are absolutely worth the money, not only making maintenance easier, but with FAR better results. It's one of those 'now, why didn't I do this sooner' moments....

Hmm that's quite a difference in spring length! That could very well be your problem, let us know if it fixes the issue!

 

[Charlie98]

Hmm that's quite a difference in spring length! That could very well be your problem, let us know if it fixes the issue!

Well... I expect the new buffer and buffer spring to completely fix the issue. Remember, the last range session I had a brand new bolt in... and I still got jams. I really think the gas system is overdriving the BCG. The H1 buffer and new spring will validate that... or not.

 

[Varminterror]

Backwards facing spent cases in the failure to eject mode in AR’s is most typically excessive bolt travel. The bolt face is hauling ass backwards and the extractor has ahold of the case rim, but if the bolt face can retract too far behind the rear edge of the ejection port, the side of the case smacks the port rim, imparting spin onto the case and bouncing the tail forward (and back into the action, since the casehead represents most of the mass of the case), so then we end up with empty cases sitting backwards in the action.

This is obviously exacerbated by excessive carrier speed and carrier bounce at the rear - meaning the case is moving faster backwards and then the carrier bounces off of the buffer tube and comes back faster than it should too. Low spring rate, low reciprocating mass, and over-gassing contribute to excessive carrier speed, but typically, if the case isn’t smacking the port rim and bouncing into a spin, then they’ll find their way out of the port one way or another when the carrier starts forward again, as they should. So it’s really that dimensional issue of boltface displacement behind the rear edge of the port which causes cases to spin around backwards.

Not always, but often, this reveals itself as small dents on the side of the lower body of the case, and or worn finish on the inside corner of the ejection port.

Replacing the buffer tube, replacing the buffer bumper, or adding shims is typically the best solution here.

 

[lysanderxiii]

Hmm that's quite a difference in spring length! That could very well be your problem, let us know if it fixes the issue!

Well... I expect the new buffer and buffer spring to completely fix the issue. Remember, the last range session I had a brand new bolt in... and I still got jams. I really think the gas system is overdriving the BCG. The H1 buffer and new spring will validate that... or not.

The top one only has 24 coils.

The bottom one has the correct 27 coils.

 

[Charlie98]

Replacing the buffer tube, replacing the buffer bumper, or adding shims is typically the best solution here.

Adding shims to.... what?

The top one only has 24 coils.

I wondered about that. I did clean the spring channel... I did not find anything besides fouling, that is to say, no broken spring coils.

Backwards facing spent cases in the failure to eject mode in AR’s is most typically excessive bolt travel.

That's kind of what all the pointers are leading me to... that's why I changed both the buffer and buffer spring. I installed the H1, just to see if it will make a difference, but I'll have my Standard buffer with me in case it goes the opposite direction. For that matter, I'll have my original bolt, too, and I may install that just to see what shakes out.

 

[Varminterror]

Adding shims to.... what?

The buffer, inside the buffer tube. Just be sure to drill a vent hole in the center.

That's kind of what all the pointers are leading me to... that's why I changed both the buffer and buffer spring. I installed the H1, just to see if it will make a difference, but I'll have my Standard buffer with me in case it goes the opposite direction.

I said in my post “excessive bolt TRAVEL,” which is NOT the same thing as “excessive bolt SPEED”. Changing the buffer and spring will do nothing at all to the dead length of the buffer tube. If you would read the rest of my post above, I described the physical position problem. The only possible way a buffer change can influence this problem is if your existing buffer bumper is cut too short or worn. Most commonly, it’s an issue of improper dimensions on the buffer tube.

if the bolt face can retract too far behind the rear edge of the ejection port, the side of the case smacks the port rim, imparting spin onto the case and bouncing the tail forward (and back into the action,

I have lead the horse to water here, but I can’t make it think. Check your bolt face position relative to the ejection port with the bolt pulled to its most rearward position (aka, buffer bumper pulled all the way against the buffer tube. Excessive bolt SPEED makes excessive bolt TRAVEL symptoms worse, but the two issues are independent, and without the excessive bolt travel behind the port rim, these backwards case failures really don’t happen - ejectors and extractors flick cases out of the action, they do NOT spin cases around while the action is open. The ONLY failure mode which makes that happen is when the case bounces off of the port at the rear because the bolt is traveling too far rearward - again, the bolt face should only clear the bolt stop by 100-120thou.

Excessive bolt travel has a few culprits, most commonly buffer tubes too long, which is more frequent these days as more buffer tube design options are available (A5, etc). Something worth noting - you may want to confirm your gas key isn’t running into your lower, which will become the “rear stop” for the reciprocating mass if the buffer/bumper isn’t long enough to stop the bolt travel at the end of the receiver extension (aka buffer tube) before the gas key hits the lower, potentially damaging both parts. If it’s making contact, with the upper pivoted or removed, you will see dents in the front face of the top of the lower receiver ring, where the buffer tube screws into the lower, and usually finish witness on the gas key.

We can also see this happening if the extractor isn’t traveling or otherwise not letting go of the case rim, but typically this only yields stovepipes, not backwards case jams. The ONLY way cases end up backwards is if something smacks them in the side to spin them around and INTO the action (aka, not the shell deflector).

This issue, among only a few particular others, is one of the most common reasons we see threads online citing problems with home-build AR’s. It’s part of the book of knowledge which separates “I watched some YouTube videos” and real AR builders.

 

[powermad]

It's been running for 5k rounds.
I doubt the receiver extension has grown but the bumper on the end may be smashed flat shortening it enough to long stroke.

 

[Charlie98]

I have lead the horse to water here, but I can’t make it think.

Tap the brakes there, bucko. I AM listening... but this is all new to me, and, yes, I've given it quite a bit of thought. I do appreciate your input. I'll admit, you are talking a little over my head on that last post... but I now see what you are talking about.

This issue, among only a few particular others, is one of the most common reasons we see threads online citing problems with home-build AR’s.

If you need to, circle back to my OP... this gun has run 100% for about 5000 rounds over about 10 years. This is, literally, the first diagnostic problem I've run into with it... or any other AR I have, or have built.