Correct Length for LR-308 Buffer Tube

[98Z5V]

8 minutes ago, CorpsTex said:

Better check with Aero Precision, they sell the correct buffer, buffer spring and buffer tube for a rifle length AR10. This will allow the correct bolt hold back when the magazine is empty. And yes the overall buffer length is between 5.3 to 5.5" long for proper bolt operation

 

He's running a Carbine Recoil System...   Your other numbers above are not correct. 

[CorpsTex]

Clearly stated in my first response the both AR10 builds are rifle length not carbine length builds.

 

[98Z5V]

On 3/23/2015 at 5:16 PM, majordon said:

What is the proper length for an LR-308 buffer tube? I am using a 7" mil-spec tube with DPMS 308 buffer and spring. My problem: I can't get the bolt to lock back; it appears that the the bolt doesn't trravel far enough to allow the bolt catch to activate.

 

Anyone have any opinions on this or as to what I might do to correct this?

 

Thanks from a new member. Majordon

This was the original post from this thread, and you even quote it - you responded with the response below...  The OP clearly stated that he was using a 7" receiver extension.  You then proceed to tell him that he needs a 5.300" long buffer.  Not to mention, this thread was started in March of 2015...

On 4/4/2020 at 5:01 AM, CorpsTex said:

Your buffer is too long, I have a few AR10's. The correct overall length of your buffer should be 5.300 inches. With a overall spring length of 12.5". I encounter the same problem during my second build. Bolt carrier would not properly latch on the bolt catch. These builds are both rifle length builds not carbine with Magpul full length rifle stocks with extended recoil pads attached.

Doesn't matter that you are using Rifle Recoil System Components. Doesn't matter.  You used that info to correct a guy that is using Carbine Recoil System Components.  Are you getting that yet?  Is that sinking in?  You directly told a guy with a Carbine Recoil System that he needed a Rifle buffer, which will never, ever work.  And, research your numbers.  This is a good place to start:

http://heavybuffers.com/reference.html

Edited April 12, 2020 by 98Z5V

[CorpsTex]

Clearly stated in my first response the both AR10 builds are rifle length not carbine length builds.

Check with Wing Tactical they carry all buffer length in both Carbine length and Rifle length, 2.5" carbine and 5.3" for rifle length. He can only fix his own problem with a little time of web searching for the correct parts for his AR to function correctly. Without any body else's input.

[DNP]

Rifle gas is not rifle buffer. I think there’s some confusion going on here with your thoughts.  The recoil system and the gas system are two different deals. A 5.3” buffer in a 7” tube only leaves you with 1.7” of travel. How long is your BCG?  Think about that. 

[Matt.Cross]

27 minutes ago, DNP said:

Rifle gas is not rifle buffer. I think there’s some confusion going on here with your thoughts.  The recoil system and the gas system are two different deals. A 5.3” buffer in a 7” tube only leaves you with 1.7” of travel. How long is your BCG?  Think about that. 

Yep, and a 308 round itself is 2.800" long, so you have to have that much travel at a bare minimum...

[dean]

if the bolt will not go far enough to the rear and you have the proper buffer, than your( a AR 5.56 sp

ring? ) spring is to long,  i had same thing with a lr308 build, i cut my spring to just under ten inches and it works as advertised

[98Z5V]

^^^   That's bad advice, and I wouldn't be telling anyone to do that.

[jtallen83]

17 hours ago, dean said:

i cut my spring to just under ten inches and it works as advertised

Then there is something else wrong with your rifle. 

[Radpilot]

Your buffer tube is too short it should be

7 7/8  for the 308 carbine, I have experienced the same problem before , Play around spraying in the buffer weights To fine-tune it

[unforgiven]

Or get the Armalite recoil system and go shooting. Just my 2 mags

[98Z5V]

19 hours ago, Radpilot said:

Your buffer tube is too short it should be

7 7/8  for the 308 carbine, I have experienced the same problem before , Play around spraying in the buffer weights To fine-tune it

This thread is becoming just PACKED with bad information, all the way around.

Correct internal depth for a real AR-10 Carbine Receiver extension is 7 5/8".  Not 7 7/8" - that would be 1/4" out of spec, right there.  Bad advice.

Correct internal depth on a DPMS LR-308-based carbine extension would be - proper AR15 carbine receiver extension depth.  The real number is 6 15/16" internal depth.  The commercial, industry standard has be 7.000" internal, with no ill effects.

^^^   That's the real data, right there.

Edited March 22, 2022 by 98Z5V

[DNP]

You leave us alone for a couple days and look how boogered up we can make things. 

[Tex]

Hello 2022, 2024 here: this thread has been great. I just received my 22 inch, rifle+2 gas and was wondering if that would change any of the spring/buffer combo. I'm looking to go with a LR308 carbine 7 7/8 tube and a carbine buffer. (Aero M5 upper/lower) Not sure what weight of buffer to start out with.

If anyone has any info as far as the +2 rifle system I would greatly appreciate the feedback. 

If its any help as for the gas port size, the barrel is an Odin 22in 6.5 cm and it came with the gas block installed. I could pull it off and measure, but all I have is calipers so it would be a rough dimension. 

 

Thank you all 

[Armed Eye Doc]

On 9/6/2024 at 8:43 PM, Tex said:

carbine 7 7/8 tube

The correct length is 7 5/8.  If you want the 7 5/8 tube, be sure to get either a true Armalite tube or a VLTOR A5 tube.  Those will be the correct length.  Others may or may not be correct.

As for a buffer, start with a standard AR-15 sized H3 buffer.  It will be 5.4 oz (maybe 5.6, I don't remember off the top of my head).  That will get you what you want for the buffer.

You also want to get an Armalite AR-10 spring or Sprinco orange spring to have the correct spring.

[shooterrex]

^^^^ what he said. The +2 gas tube length has NOTHING to do with the recoil  system. 

[98Z5V]

On 9/27/2024 at 2:16 PM, Armed Eye Doc said:

You also want to get an Armalite AR-10 spring or Sprinco orange spring to have the correct spring.

Sprinco RED spring is the equivalent of the Armalite EA1095 spring.  The Sprinco ORANGE spring is what you need for running 7.000 internal depth AR15 Carbine Receiver Extensions with the shorty 2.500" buffers.  7 5/8" internal depth carbine receiver extension, AR15 Carbine H3 buffer that weighs 5.4 oz and is 3.250" long, and the Armalite EA1095 spring, or the Sprinco RED spring.  That's the setup for a proper recoil system in most Large Frame ARs of common caliber.  Gas system comes next, after that is solved. 

On 9/27/2024 at 2:20 PM, shooterrex said:

^^^^ what he said. The +2 gas tube length has NOTHING to do with the recoil  system. 

Truth ^^^^.  After solving the recoil system, you solve the gas system.  Those two systems are independent, but must work together...  Solve recoil first, get it straight, and the rest is easy.

Edited November 13 by 98Z5V