Carbine VS Rifle Buffer

[daddoz777]

Carbine vs. rifle buffer assembly. Everybody says they know what they're talking about but I believe few people really do. The question is whether the buffer assembly type has a correlation to the gas length, specifically on an AR10/.308.

There appear to be two dogmatic camps:

1. Buffer assembly (carbine or rifle) and gas system (carbine, mid or rifle) must match.
2. Buffer assembly only has to do with the type of stock that is used (adjustable M4 vs. fixed A2) and has nothing to do with gas tube length.

I just got off a chat this morning with Aero Precision and they are telling me the buffer assembly needs to match the gas system. Here's what they wrote:

(8:55:17 AM) Zach : On the M5 it is strongly
advised that you match the gas system with the buffer system for the best
reliability. For instance rifle gas tube with rifle buffer system. If you cross
the carbine buffer system with the rifle gas system it will not generate enough
pressure to get the BCG all the way back and cause Failure to feed and extract
issues as well as failure to last round bolt hold open.

Some people agree, while others are certain it makes no difference. I write this because I built a .308 AR and am having trouble with it cycling (won't blow the bolt back and eject the spent casing). Here's my setup:

• Aero Precision M5 .308 upper
• Aero Precision M5 .308 lower
• Aero Precision M5 .308 Enhanced Carbine Buffer Kit
• Diamondback AR-308 18" Barrel with Rifle Length Gas Port
• Adjustable Gas Block
• Rifle Length Gas Tube
• Generic AR-10/.308 BCG

The gas tube sits correctly into the bolt carrier key and there are no blockages between the bolt and barrel gas port. Key is staked and solid with no leaks. Air blown into the gas key actuates the bolt (IE no blockage there). I've also been experimenting with opening up the adjustable gas block but it doesn't seem to make any difference. And at nearly $1 per round I really need to be systematic to minimize wasted shots.

Constructive discussion appreciated.

Thanks all!

Dan

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[Koda]

I had the same question as I just built an AR15 rifle with carbine buffer. Lots of people run rifle length gas systems in the AR15 with a carbine length buffer without issue. I dont know about AR10s builds.
My guess is with an adjustable gas block and maybe the right buffer weigh it should be fine?

 

[solv3nt]

Every action has an equal and opposite reaction; act accordingly.

 

[Cerberus Group]

Sig 716 308 run a standard AR-15 type buffer system.

Me thinks the Aero person was reading from a script.

 

[daddoz777]

I had the same question as I just built an AR15 rifle with carbine buffer. Lots of people run rifle length gas systems in the AR15 with a carbine length buffer without issue. I dont know about AR10s builds.
My guess is with an adjustable gas block and maybe the right buffer weigh it should be fine?

I know, right? My AR15 with a mid-length gas port and a "carbine" buffer runs like a top. While there's lots of discussion about using heavier buffers for short barrels you never hear any discussion on this topic when it comes to AR15s (at least not that I've seen).

 

[Cerberus Group]

You can run either with either buffer systems, just make sure the system is balanced so it doesn't batter itself.

Not a fan of adjustable gas blocks, but find them mandatory on AR-10s, as there's so many variables in loadings for 308.

Make sure you turn the adjuster screw on the block now and then, or you'll end up with a non-adjustable gas block. Also over time the carbon can eat some of the internal adjustment mechanism. If the AR-15 rifle is setup properly, you shouldn't need an adjustable gas block...with or without a can.

 

[titsonritz]

You can keep them both, I'll stick with the A5 system.

 

[Cerberus Group]

You can keep them both, I'll stick with the A5 system.

Yep, and can run the A5 with both rifle types/calibers

 

[Koda]

Make sure you turn the adjuster screw on the block now and then, or you'll end up with a non-adjustable gas block. Also over time the carbon can eat some of the internal adjustment mechanism.

not something I thought about before, but good to know. Carbon buildup on the threads...!

 

[titsonritz]

(8:55:17 AM) Zach : On the M5 it is strongly
advised that you match the gas system with the buffer system for the best
reliability. For instance rifle gas tube with rifle buffer system. If you cross
the carbine buffer system with the rifle gas system it will not generate enough
pressure to get the BCG all the way back and cause Failure to feed and extract
issues as well as failure to last round bolt hold open.

As Brandon would say, that is a bunch of malarkey, it all boils down to the size of the gas port. Something to keep in mind about adjustable gas blocks, they will only decrease your available gas they are incapable of increasing it.

 

[titsonritz]

not something I thought about before, but good to know. Carbon buildup on the threads...!

I was going to mention that too you on hand guard thread when you mentioned setting and leaving it, may as well have a standard gas block.

 

[Koda]

I was going to mention that too you on hand guard thread when you mentioned setting and leaving it, may as well have a standard gas block.

yup, that hit me when I read Cerberus's comment. Not to hijack this thread but I will have to figure something out how often I need to remove the handguard just to exercise the screw.

As for on topic, my 223 AR runs a rifle length gas system with a carbine buffer assembly just fine. I did need to buy the next heaviest buffer weight to eliminate some light extractor clawing.

 

[msgriff]

Over-gassed/over-speed is often misdiagnosed as under-gassed.

 

[daddoz777]

Over-gassed/over-speed is often misdiagnosed as under-gassed.

My wife would say I'm over-gassed.

 

[ValleyAR]

my first troubleshooting would be the gas block or bcg (the bcg's ride as well), going between dpms and ar10 buffer configs wouldnt matter that much Imo, atleast for basic weapon cycling.

id prolly try a standard gas block first, especially if the bcgs ride into the buffer tube is nice and smooth (while holding in a firing orientation).

 

[ValleyAR]

yup, that hit me when I read Cerberus's comment. Not to hijack this thread but I will have to figure something out how often I need to remove the handguard just to exercise the screw.

As for on topic, my 223 AR runs a rifle length gas system with a carbine buffer assembly just fine. I did need to buy the next heaviest buffer weight to eliminate some light extractor clawing.

for ar308

Dpms buffer config: ar15 carbine length tube, 2.5" shorty buffer, rifle spring
ar10 buffer config: a5 length buffer tube, 3.25" standard carbine ar15 buffer, rifle spring.

if you do the math its the same travel distance in either config.



here is a nice breakdown i saved while doing research

AR-10 Buffer

Good morning Everyone! I know there is a buffer question on here already. But it doesn't answer my question. What determines the best buffer weight and spring length? I am thinking about buying an 18" barrel with mid-lentgh gas port for my AR-10 build. Can I use a carbine buffer and spring with t...

forum.308ar.com

 

[daddoz777]

my first troubleshooting would be the gas block or bcg (the bcg's ride as well), going between dpms and ar10 buffer configs wouldnt matter that much Imo, atleast for basic weapon cycling.

id prolly try a standard gas block first, especially if the bcgs ride into the buffer tube is nice and smooth (while holding in a firing orientation).

Yeah, I'm considering a fixed non-adjustable gas block just to eliminate that out of the equation.

 

[daddoz777]

As Brandon would say, that is a bunch of malarkey, it all boils down to the size of the gas port. Something to keep in mind about adjustable gas blocks, they will only decrease your available gas they are incapable of increasing it.

I just measured my gas port at about .062". According to what I'm seeing on a cursory Google search it should be about .096" for an 18" .308 rifle length barrel. WHOA am I missing something here???

 

[Cerberus Group]

I just measured my gas port at about .062". According to what I'm seeing on a cursory Google search it should be about .096" for an 18" .308 rifle length barrel. WHOA am I missing something here???

Did you use a pin gauge?

 

[Snip]

I tried to use a carbine buffer in a M5 rifle system Couldn't get it to function reliably by adjusting the AGB. Once I got a rifle buffer, system worked like a charm. No need to drill out gas port.