AR-10 Buffer Issues/Questions

[wes.crockett]

Hello all,

I just picked up my rifle from my smith. I brought the pieces in and left with an ALMOST done rifle. He said he was unable to get it to cycle. It would fire, but not load the next round. I'm not sure if it was also failing to eject.

It may be the cheap buffer/spring that I had purchased or the BCG that I received for free... Although I am a bit frustrated (at the situation, not my smith) I need to start with one, see if it fixes it, then try another.

With the spring and buffer being the less expensive to troubleshoot, I figured I would start there. I made the unfortunate, and uninformed, decision to buy a Guntec LR308 Carbine buffer. I should note that I am running a 20" barrel. From what I read, I should be OK with a carbine buffer/tube set up with it though.

As I can't find any DPMS brand buffer springs and buffers, I need recommendations (reasonably priced... I can't spend $100 on a buffer.)

I found the Sprinco Orange spring. Does anyone know about these? It can be seen here: http://www.sprinco.com/tactical.html

Here is the description:

Tactical Springs LLC .308 M4 CARBINE Extension Tube EXTRA POWER Moly-Plated Chrome Silicon Buffer Spring in Hard Tube (Color Coded ORANGE) [NOTE: Originally Developed for .308 CARBINE Platforms Utilizing Standard 7" Depth M4 Carbine Extension Tubes with Short Buffers. E.G. DPMS/Bushmaster, Etc., but are Often Appropriate for any Severely Overgassed Carbine of Similar or Lesser Calibers]

Any and all help would be greatly appreciated.

Thanks,
Wes

[Intimid8tor]

Step one is to go shoot it and describe completely what it is doing.

Is it failing to eject, failing to load a round from mag, failing in some other respect.

I'm sorry, but your Smith should have been able to troubleshoot and accurately describe what is happening and recommended a course of action. To just give it back and shrug their shoulders is kind of a waste.

It sounds like they aren't a smith, but maybe just a gun shop.

Sent from my SM-G920V using Tapatalk

[Spyder]

I'm (not really) surprised that a "smith" would let a known malfunctioning gun out of their shop. Take it back and tell them to fix it. It's what you paid for.

[waawaaweenie]

I was advised to use a factory Armalite buffer and spring in my 308 AR by Slash who makes excellent buffers and it has cycled perfectly. I am using a rifle length butt stock

[nate76239]

The orange spring on the link provided looks correct. I have used a couple of smaller springs and detents from Guntec, I'm not sure the buffer is the problem yet. Intimid8tor is right the problem is not described well enough yet there could be another problem like bcg gas key leaking that can also cause cycling issues. See if there is another cal gunner in your area that you may be able to meet at a range who has a working lower you can test with before buying parts that may not address the problem.

[Spyder]

Or take it back to the person you paid to make it work.

[wes.crockett]

I realize fully that the LGS/Smith probably should have worked through the problem. I know, for fact, that they are qualified at what they do as they manufacture AR's from bare metal in their shop. So it isn't a question of their ability to assemble an AR. I know that I bought/was gifted some cheap parts so until I replace those parts and STILL have an issue, I'm not pinning it on them. Truth is, I forgot to ask if it was FTE or FTL. I have the rifle in hand so I can answer questions that can be answered through visual inspection.

He did explain that the spring and buffer I have are very poor quality which, upon some research, I can't deny. The buffer is actually just a weight (when shaking, no parts internally move.) So, I want to replace the buffer and spring first as they are the most likely culprits.

He said that, when I get another spring/buffer, I can bring it back in to try cycling it in their indoor testing aria (saves a ton of money in this process due to range fees and the 45 minute drive to get to the nearest rifle range.)

Which buffers do you guys trust in an AR-10 rifle running in a carbine configuration?

I just followed up with the gunsmith. It was both FTE and FTL

[SloChicken]

you can use a carbine length buffer tube but you need a 3.5" buffer and it is quite helpful to have a .308 spring (it has more coils and as a result is a higher rate).

Your rifle, in all likelihood has too long of a buffer and it is interfering with the BCG cycling back far enough to get behind the next round and as a result it can't pick it up. Viola, FTF.

[mif_slim]

So you mixed an AR-10 upper/lower with a LR 308 buffer end? Make sure its all AR-10 parts or all LR 308 parts.

I cant answer for AR10 but an LR308 variant, you can use a AR15 buffer with LR308 buffer spring and buffer which is different length from an AR10.

Curious, does the bolt lock back when you pull he charging handle? I know this isnt the right way to fix it but my lr308 buffer spring was a tad long. I cut off two coils and stretched the spring to counter the loss of coil. It locked back and when i went to shoot it, it cycles fine.

[wes.crockett]

So you mixed an AR-10 upper/lower with a LR 308 buffer end? Make sure its all AR-10 parts or all LR 308 parts.

I cant answer for AR10 but an LR308 variant, you can use a AR15 buffer with LR308 buffer spring and buffer which is different length from an AR10.

Curious, does the bolt lock back when you pull he charging handle? I know this isnt the right way to fix it but my lr308 buffer spring was a tad long. I cut off two coils and stretched the spring to counter the loss of coil. It locked back and when i went to shoot it, it cycles fine.

I don't think i mixed parts, but am not 100% sure. When i pull back, yes, the bolt stays back until I hit the bolt release. It does feel quite a hard pull to get it back though.

[SloChicken]

... He did explain that the spring and buffer I have are very poor quality which, upon some research, I can't deny. The buffer is actually just a weight (when shaking, no parts internally move.) So, I want to replace the buffer and spring first as they are the most likely culprits.

He said that, when I get another spring/buffer, I can bring it back in to try cycling it in their indoor testing aria (saves a ton of money in this process due to range fees and the 45 minute drive to get to the nearest rifle range.)

Which buffers do you guys trust in an AR-10 rifle running in a carbine configuration?

I just followed up with the gunsmith. It was both FTE and FTL

not sure how you can have a crappy buffer or spring ...

The buffer is merely a weight. (except for the weights sliding and making a secondary moment of inertia)

The spring, again is much the same. Pretty hard to have a crappy one. You can have one that is an inappropriate rate for the gas charge on the BCG and/or the weight of the buffer. But that doesn't make the spring crappy, just the mechanic ...

The buffer has to be short enough to allow the bolt to recoil enough to get behind the next round (and the bolt stop as well ...) or it is too long. All AR 15 buffers are too long (I cannot speak to the AR10 config as I don't run them - they are longer, and that is all I can say).
You need a shorter buffer to allow the BCG to come rearward under the gas charge, and in turn you need a spring/buffer combo that can handle the recoil and also return the BCG home.

And that is the simple math of it.

For me, a 3.5" buffer, a .308 carbine spring works fine. Play with the gas via an adjustable gas block, or add/remove weights from the buffer. Pretty much that is how to tune.

Last, be sure to slather the whole rifle in froglube for best results.









lol, kidding about the Froglube ...

[wes.crockett]

not sure how you can have a crappy buffer or spring ...

The buffer is merely a weight. (except for the weights sliding and making a secondary moment of inertia)

The spring, again is much the same. Pretty hard to have a crappy one. You can have one that is an inappropriate rate for the gas charge on the BCG and/or the weight of the buffer. But that doesn't make the spring crappy, just the mechanic ...

The buffer has to be short enough to allow the bolt to recoil enough to get behind the next round (and the bolt stop as well ...) or it is too long. All AR 15 buffers are too long (I cannot speak to the AR10 config as I don't run them - they are longer, and that is all I can say).
You need a shorter buffer to allow the BCG to come rearward under the gas charge, and in turn you need a spring/buffer combo that can handle the recoil and also return the BCG home.

And that is the simple math of it.

For me, a 3.5" buffer, a .308 carbine spring works fine. Play with the gas via an adjustable gas block, or add/remove weights from the buffer. Pretty much that is how to tune.

Last, be sure to slather the whole rifle in froglube for best results.


lol, kidding about the Froglube ...

So it is a 2.5" buffer but when i shake it, there is no internal movement as you suggest, and the smith pointed this out to me as well.

[wes.crockett]

So, I am meeting a buddy and the smith at the shop tomorrow and we will try another BCG. After talking through it, that is what it sounds like. Hopefully we can troubleshoot it enough to know tomorrow.

[mif_slim]

Well if the bolt locks back then it cam be something else. Check the gas port the barrel maker might of made it smaller??

[wes.crockett]

Well if the bolt locks back then it cam be something else. Check the gas port the barrel maker might of made it smaller??

Possible. After the last round in a magazine, the bold does not lock back on it's own. It will lock back when using the charging handle.