AR10 Ejection Issue

[cpmiller22]

Hi all-

I'm having an issue with my DPMS style .308 that I'm hoping someone might be able to help me with. So when I initially built it, I put on a DPMS adjustable stock with a carbine length buffer, tube, and spring. With this configuration my rifle was shooting great. A few months ago I bought a nice PRS stock for my rifle. I bought a rifle length buffer, spring and tube and got everything assembled. I initially thought the rifle fired fine when I took it to the range, but realized after the first shot that it didn't actually eject the empty round and load a new one. I can use the charging handle and manually cycle it, but it just will not cycle properly on its own. A few times the BCG would feel stuck (i.e. I couldn't cycle it with the charging handle). If I took the magazine out I can always get it to clear with a good hard pull. Clearly I don't want to go back to the cheaper carbine stock for my nice rifle, but I'm not sure how to fix the problem. Any ideas would be much appreciated. I can post pictures if there is anything that would be helpful.

Thanks!

 

[PiggiePluggin]

Do you have an adjustable gas block? If so maybe try opening it a little because it's going to take a little more pressure to cycle the bcg and everything back. You may need a weaker spring or lighter buffer if you can't adjust the gas.

With the change of the tube and stock, I'd say it's a weight/pressure issue, but you could check to make sure the ejector isn't fouled up and stuck inside the bolt. I've seen a little sliver of brass deadline my bolt before. Try loading one round in the mag and see if it locks back on the catch with the brass on the bolt face. If so, your bolt could need fixing.

Are you shooting the same rounds? My jp gas reg is set to shoot 168 gr fgmm. I intentionally set it that way for minimal recoil impulse and to minimize wear and tear on the rifle. if I use 175 gr rounds, I have to open the reg 1/4 turn otherwise the same thing you are experiencing happens due to the pressure change from the rounds. To make a long story short, it sounds like the gun is not pushing the bolt back far enough to completely go through all the stages of firing, it's getting stuck in the "unlocking" or "ejecting" phase. When you say you couldn't manually cycle the rifle, was that because there was a double feed and the gun tried to feed the empty casing stuck on the bolt face, and a new round into the chamber causing it to jam up? It sounds like it's very close to cycling correctly. I've never done it, nor condone doing it, but I've heard of people cutting off 1 coil of the buffer spring at a time to get their bolts to cycle properly. Easy fix, no need to go back to your old stock, possibly need a new spring or buffer, or even easier a ¼ turn to the regulator to open it a little, that's all.

Also, if you are putting lube or cleaning solvents down the gas tube, that will do it as well. It causes fouling inside the tube and essentially acting like a choke on a lawn mower engine. This same thing can happen if you are one to subscribe to plugging your barrel and filling it with bore foam or something like that. It finds its way into the gas tube and does the same thing.

 

[jaycoux]

Easy fix. Buy a spacer that will allow you to run the old carbine buffer and spring in your rifle length buffer tube. Same exact thing happened to me on a PredatOBR. Went back to the stock setup with a spacer and voila....ran just fine.

 

[PiggiePluggin]

That will work as well.

 

[samnev]

I have an AR10A4 that I put the PRS stock on it with DPMS A2 receiver extension, buffer and spring. Never had a problem. Did you by any chance not use the supplied Magpul screw when you installed the PRS. The PRS stock will cause the issues you described without that screw.

 

[-Nick-]

I A few times the BCG would feel stuck (i.e. I couldn't cycle it with the charging handle). If I took the magazine out I can always get it to clear with a good hard pull.

That right there needs a LOT of clarification since it's the likelier culprit. Are you saying the BCG is stuck closed with a spent round in the chamber? Or are you saying when you try to charge it there's resistance and it's getting stuck in the buffer tube? If it's the first then you might have an overly tight throat or ammunition issues and not likely gassing or buffer. I know you tried to be detailed but a little more will go a long way here.

 

[PiggiePluggin]

Agreed on the more info part, can you tell us if the bolt is locked into battery when it's hard to cycle? He said the problem started with the new tube and stock, so for me, that would rule out throat specs unless with the stock change he decided to change ammo too

 

[jaycoux]

All you have to do is think about what changes you made to the rifle. It worked fine before, what is different? Start there...

 

[PopSmoke]

Clean it well, go back and video with the PRS. Focus on the ejection port and angle your camera towards where the BCG would clear to strip the next round out of the mag. Clean it again and go back to the original stock, film the same way. Chances are your change on the tube may be the culprit.

If the problem persists, especially if it is the LR-308, you will want to check the gas block. Many of the LR's had sloppy gas blocks and leaked badly. So badly that I couldn't get 168 grain match ammo to cycle.

But, since you said the mag being released freed up the BCG, you might use a different mag.

 

[cpmiller22]

Thanks for all the ideas. First off, I don't have an adjustable gas block, and I don't think it's leaking because it was working fine with the carbine stock. I was thinking perhaps a good test would be to put my carbine spring in with my rifle buffer and buffer tube. My hypothesis is that it should fix the ejection problem, but may result in the bcg not closing all the way after cycling. If this works than I can work on trimming my rifle length spring to reduce the tension enough to allow the rifle to cycle. Hopefully I can get to the range in the week or so and conduct some testing.

 

[EXTREMEPREJUDICE]

That right there needs a LOT of clarification since it's the likelier culprit.

Absolutely, I've never seen a buffer/spring too strong to manually cycle................something else has gotten buggered up when you swapped the components out. Guessing the BCG but...........................

 

[-Nick-]

Thanks for all the ideas. First off, I don't have an adjustable gas block, and I don't think it's leaking because it was working fine with the carbine stock. I was thinking perhaps a good test would be to put my carbine spring in with my rifle buffer and buffer tube. My hypothesis is that it should fix the ejection problem, but may result in the bcg not closing all the way after cycling. If this works than I can work on trimming my rifle length spring to reduce the tension enough to allow the rifle to cycle. Hopefully I can get to the range in the week or so and conduct some testing.

Lol... Or you could also clarify what was asked earlier in regards to the BCG getting stuck. Again... Is the BCG getting stuck in the closed position with a fired case in the chamber? You said earlier it would get stuck and you wouldn't be able to even manually cycle it. That means it has nothing to do with the gas but more likely the ammo or throat. Is it partially loading a new cartridge but not going into battery? You might have a dented gas key and not realize it. You can spend a lot of time swapping around parts and wasting ammo while getting frustrated (I think most of us have been there at some point) or clarify certain points you made earlier which might make curing the issue cheaper and easier...

 

[LRRPF52]

What "rifle" buffer did you use when you installed the PRS? They are shorter for AR10's than AR15's, so an AR15 rifle buffer would cause the exact condition you describe. It's a very common mistake when installing a rifle length RE from a carbine on AR10's.

 

[LawnMM]

Lube the carrier and bolt up. If the bolt dries out it will start to stick in the carrier sometimes which can cause cycling problems and difficult charging.

 

[LRRPF52]

He went from a functioning gun with no issues, to a non-functioning gun after installing a PRS, and I am seeing recommendations for adjustable gas blocks, lubrication, amateur guesses as to what the problem is, with no shortage of knee-jerk, cut and paste solutions that others have recommended for totally different situations.

If the correct components were installed with the PRS, there would be no problems with a gun that was running fine before. OP says,

I bought a rifle length buffer, spring and tube and got everything assembled. I initially thought the rifle fired fine when I took it to the range, but realized after the first shot that it didn't actually eject the empty round and load a new one.

His problems are symptomatic of an AR15 rifle buffer installed in an AR10.

 

[dmike]

Posts 3, 13 & 15. I'm with LRRPF52

 

[-Nick-]

He went from a functioning gun with no issues, to a non-functioning gun after installing a PRS, and I am seeing recommendations for adjustable gas blocks, lubrication, amateur guesses as to what the problem is, with no shortage of knee-jerk, cut and paste solutions that others have recommended for totally different situations.

If the correct components were installed with the PRS, there would be no problems with a gun that was running fine before. OP says,



His problems are symptomatic of an AR15 rifle buffer installed in an AR10.

Except for none of those changes would cause the BCG to get stuck closed in battery...

 

[dmike]

Except for none of those changes would cause the BCG to get stuck closed in battery...

uhhh...dammit

 

[LawnMM]

Lube the carrier and bolt up. If the bolt dries out it will start to stick in the carrier sometimes which can cause cycling problems and difficult charging.

To elaborate, if the bolt isn't sliding forward and rearward freely because its gummed up with carbon and not sloppy wet, the bolt won't unlock after firing and you'll have trouble getting the bolt to unlock and cycle. That won't necessarily explain a non ejected round unless its really shitty inside. Try this...lock the bolt back by hand, no mag in the gun, watch the bolt and hit the bolt release and let it slam home. Does it bounce open?

How have you been cleaning the carrier? Large frame ARs can get filthy in a hurry, that's why the emphasis on running them wet. They don't have to be clean, but they do have to be wet, when that crud starts to dry it will gum up the inner workings. I've seen it stop a bolt from camming properly which resulted in the bolt bouncing open and light strikes from an out of battery bolt, thankfully it never resulted in an out of battery detonation.

 

[-Nick-]

uhhh...dammit

Exactly lol... That's why it would be nice if we could get I don't know... more details lol

 

[cpmiller22]

Ok, I've attached some pics that might help. I noticed a few tiny pieces of brass in the barrel that you can see on the first picture which I have cleaned out. I cleaned upper and the BCG real well, and lubed then up. If I close the charging handle and manually slide the BCG in and out of locking position it seems to move pretty smoothly.

I pulled out the buffer and spring to investigate a bit more on that side. I measured the buffer and confined its an ar10 rifle buffer measuring 5 3/16" long.

Hopefully I can get to the range soon and see if the cleaning helped at all. I'm not very hopeful it will help, so I will probably try the carbine spring test I previously mentioned if it's still not cycling. I'm happy to share any additional information if it will help with solving this problem.

Thanks!

 

[dmike]

Ok, I've attached some pics that might help. I noticed a few tiny pieces of brass in the barrel that you can see on the first picture which I have cleaned out. I cleaned upper and the BCG real well, and lubed then up. If I close the charging handle and manually slide the BCG in and out of locking position it seems to move pretty smoothly.

I pulled out the buffer and spring to investigate a bit more on that side. I measured the buffer and confined its an ar10 rifle buffer measuring 5 3/16" long.

Hopefully I can get to the range soon and see if the cleaning helped at all. I'm not very hopeful it will help, so I will probably try the carbine spring test I previously mentioned if it's still not cycling. I'm happy to share any additional information if it will help with solving this problem.

Thanks!

View attachment 52046View attachment 52047View attachment 52048

Dumb question but are you able to lock the bolt to the rear?

 

[cpmiller22]

Dumb question but are you able to lock the bolt to the rear?

Yep. If I pull back the charging handle with a mag in, the bolt locks open.

 

[dmike]

Can you lock it back without a mag?

 

[cpmiller22]

Can you lock it back without a mag?

Yes. If I pull back the charging handle the bolt goes back far enough that I can push the bolt catch and it will hold the bolt open.

 

[dmike]

I'm thinking jaycoux has a solid idea with post #3 but can you think of anything that might have happened with the gas tube/key etc when you switched everything out?

Could the buffer tube be cross threaded?

Unrelated, is it definitely an ar10 prs or could it be a 15? I've made that mistake thinking it didn't matter.

Sorry I know these are random just trying to imagine what might have gone wrong.

 

[-Nick-]

Any chance you could answer the same question that I've asked several times in regards to your BCG being stuck closed since it's I don't know... a big factor in the equation.

 

[cpmiller22]

I'm thinking jaycoux has a solid idea with post #3 but can you think of anything that might have happened with the gas tube/key etc when you switched everything out?

Could the buffer tube be cross threaded?

Unrelated, is it definitely an ar10 prs or could it be a 15? I've made that mistake thinking it didn't matter.

Sorry I know these are random just trying to imagine what might have gone wrong.

I really can't think of anything else that has changed. I double checked that it is indeed an AR10 PRS, and the buffer tube is not cross threaded.

 

[cpmiller22]

Lol... Or you could also clarify what was asked earlier in regards to the BCG getting stuck. Again... Is the BCG getting stuck in the closed position with a fired case in the chamber? You said earlier it would get stuck and you wouldn't be able to even manually cycle it. That means it has nothing to do with the gas but more likely the ammo or throat. Is it partially loading a new cartridge but not going into battery? You might have a dented gas key and not realize it. You can spend a lot of time swapping around parts and wasting ammo while getting frustrated (I think most of us have been there at some point) or clarify certain points you made earlier which might make curing the issue cheaper and easier...

Hopefully some more details in response to your questions:

When shooting through a magazine, I have to manually cycle the rifle after every shot. Specifically, after I fire the bolt goes back, but does not eject the spent round, rather re-chambers it back in the locked position. Occasionally (perhaps 1 or 2 times in 10) there was significant resistance when I tried to pull back the charging handle to bring the bolt back slowing for the ejection of the spent round and loading of a new round. As a side note, the spent round always ejects nicely when I'm cycling manually with the charging handle. On these occasions removing the magazine seemed to help reduce the resistance enough to successfully pull back the charging handle. That said, most of the time the charging handle would pull back just fine with no notable resistance. Since the rifle has never properly cycled, I was thinking this intermittent sticking wasn't likely the culprit, but I'm very open and interested to your thoughts.

I'm happy to continue to provide any additional details or pics that might be helpful in solving this dilemma.

Thanks again for all the tips so far!

 

[LRRPF52]

My LR-308 had a really tight chamber, so much that full-length sized virgin brass would not extract from it, and it needed a chamber polishing badly. After that, it ran fine. Mass-produced rifle, who knows how many chambers the reamer has been used to cut, how worn it is, and what tight chamber resulted.

Reason # 1,387,256 why I don't buy factory rifles anymore. At first notice, it seems snobbish, but it really isn't. Something about wanting the rifle just to be made correctly drives my purchasing habits, after learning that mass producers don't do so well at it.

 

[jasonfaz]

Sounds like it could be an issue with bolt bounce. That could cause the issues youre seeing with the bolt not having time to rotate forward before being re-seated back into the chamber. Cutting some coils from the spring could do the trick.

It could also be a timing problem. Youve effectively added a couple ounces to your buffer weight and moved to a spring that doesnt require nearly the same percentage of compression to allow for full length of travel compared to the carbine spring. What is the length of your gas system?

 

[PiggiePluggin]

Hard to pull the expended rounds out of the chamber, or the bolt unlocks from the chamber and it binds up half way through the cycle?

Basically to my understanding this is the cycle of the gun...

It fires, it unlocks, the bcg goes back but not far enough to eject the spent round or snag a new round. It then slams the empty brass back in the chamber. You then have to cycle the t handle manually to eject the brass.

To me it sounds like a weight issue, or under gassed. That or the buffer isn't allowing the bolt to come back all the way, or you have a bad spring and it's binding up causing the same thing.

I'd eliminate one thing at a time. If you don't have a gas reg, check for regulator alignment. Did you accidentally punch the gas tube? Is there some sort of foreign debris in the stock? I'd honestly start with cutting 1/4 off a coil off at a time and see what happens. If you mess it up, it's the cheapest part to replace. Or there are companies that sell different weight springs if you don't want to cut.

Somebody with more knowledge expound on this, but would a fire forged empty casing be a tighter fit in the chamber from expansion causing the tough manual ejection?

To the op, does it bind up with a virgin round in the chamber? If so, what percentage through the firing process?

 

[maggitas]

My .02 cents.

reinstall the collapsable stock with original buffer and buffer spring. If it worked perfectly in this configuration return it to that functioning state. If the gun cycles then you know it is in the new tube, buffer, or buffer spring. You can then swap out parts one by one and eliminate the culprit.

 

[PiggiePluggin]

My .02 cents.

reinstall the collapsable stock with original buffer and buffer spring. If it worked perfectly in this configuration return it to that functioning state. If the gun cycles then you know it is in the new tube, buffer, or buffer spring. You can then swap out parts one by one and eliminate the culprit.

Do this

 

[LRRPF52]

Looking back over the original post, I see that you built the gun yourself. What gas system length and what type of gas block did you use?

If you used an aluminum gas block, remove it, toss it, and get a steel one. We need to know the gas system length and gas block type. Pics of entire rifle with detail of the gas block would be nice. Also, measure your port diameter.