Buffer tubes...

[EasyEJL]

I could use some clarification on buffer tubes. What it looks like is the AR-15 standard for mil spec is 7", and the 308 standard is 7.75". But I've seen commercial spec AR tubes as long as 7 7/8. Will that still work if I replace the buffer + spring? Or is even the regular 7" long enough?

[mrraley]

I'll see if I cant brake it down a little bit for ya...

ArmaLite receiver extension tubes info are as followes...

•.223 / .308 rifle length 9-11/16” (inside depth)

•.223 carbine length 6-15/16” (inside depth)

•.308 carbine length 7-5/8” (inside depth)

Commercial size tube O.D. - 1.165” – 1.167” (don’t use this anymore)

Military (G.I.) size tube O.D. – 1.145” – 1.147” (carbine and rifle)

BUFFER SPRINGS

•.308 buffer spring rifle and carbine length 14-1/8” max - 13-3/4" min

•.223 buffer spring rifle length 13-1/2” max – 11-3/4” min

•.223 buffer spring carbine length 11-1/4” max – 10-1/16” min

BUFFERS

•.223 rifle length 5-7/8” – weight 5.2 oz

•.308 rifle length 5-3/16” – weight 5.4 oz

•.223 carbine length 3-1/4” – weight 3.0 oz

•.308 carbine length 3-1/4” – weight 5.4 oz

[EasyEJL]

Thanks, that helps clarify it for me. Its a little rough right now finding parts at all to complete this so i'm making sure I understand what has to absolutely be a 308 part, and what may work fine as a 223 part when I do come across things in stock.

[98Z5V]

^^^ mrraley's info up there should be pinned.  <thumbsup>

[unforgiven]

Also include you'r thread brother on the cross section cut showing the physicall difference in buffer tube.Then you got the tottal package. <thumbsup>

[edgecrusher]

Yes, what Rene said Tom, it clearly shows how much thinner a commercial tube is at the threads.

[SpookyEng]

^^^ mrraley's info up there should be pinned.  <thumbsup>

I second that!

[shibiwan]

The information is now outdated. Missing is the shorter "LR-308" length buffer that is used in DPMS pattern 308's with a standard carbine extension.

[98Z5V]

Bull$hit.

Edited November 6, 2014 by 98Z5V

[shibiwan]

DPMS Specs for .308 carbine buffer using standard 7" carbine buffer tube:

 

.308 Carbine Length Buffer length: 2.485" or in between 2 1/2 to 2 3/8

Weight .238 pounds = 3.80800 ounces

 

Therefore earlier posted info is not correct.

[98Z5V]

The information is now outdated.

 

 

This is the bull$hit part. 

 

Mrraley was the Chief Armorer at Armalite at the time of his post, and he's talking about Armalite parts, specifically, in this thread.  He's not talking about any DMPS-based parts in the least.

 

DPMS-based parts aren't even relevant to what he was conveying.

 

Nothing "outdated" about his information at all, man. 

[Birddog57]

Thanks for all your help. You guys were very helpful.

[txchl]

Will someone tell me the

a.- length of the DPMS-LR308 buffer tube

b- Length and # of rings on buffer spring

c- Length and weight of buffer

Thx

[guruofhotrod]

The answers to questions #b & c are here: http://forum.308ar.com/topic/597-buffer-tube-buffer-and-buffer-spring/

To answer your first question, DPMS 308's normally use the same buffer tubes as AR15's - BUT, you can use the

Armalite buffer system AS LONG AS you use ALL Armalite components - Buffer Tube, Buffer, and Spring - just

don't mix parts from the two (Armalite & DPMS Type) or Carbine and Rifle length

[xxlfitness@yahoo.com]

Im new to this forum and 308/7.62. I have lots of experience with AR .556 platforms. I need some help building my first 308 AR.

I read this thread and have some questions. there is much talk of different brands, when piecing one togther from scratch, how

do

you know what info applies to my build? Mine is a carbine length as far as the gas system. But you guys are referring to the stock and tube in terms of carbine vs rifle use also and I'm confused by that. My lower is a basic PSA-10 and the upper is a DPMS LR 308 Oracle A3.

The only thing I am lacking finishing it is the buffer/stock spring assembly.

Here is something below that I posted sometime back and never got an answer:

 

 

"I am confused. 
I don't understand the buffers from 3oz-7oz which is right?
I don't understand the tube length issue and the spring. Does it need a longer or stronger spring?.
I'm assuming the normal buffer for a 308 is a longer tube and longer buffer and maybe heavier buffer.
It looks like possibly you are able to use a standard length mil spec tube on it IF you use a special spring and short and heavy buffer?? help

 

 

[shepp]

10 minutes ago, xxlfitness@yahoo.com said:

Im new to this forum and 308/7.62. I have lots of experience with AR .556 platforms. I need some help building my first 308 AR.

I read this thread and have some questions. there is much talk of different brands, when piecing one togther from scratch, how

do

you know what info applies to my build? Mine is a carbine length as far as the gas system. But you guys are referring to the stock and tube in terms of carbine vs rifle use also and I'm confused by that. My lower is a basic PSA-10 and the upper is a DPMS LR 308 Oracle A3.

The only thing I am lacking finishing it is the buffer/stock spring assembly.

Here is something below that I posted sometime back and never got an answer:

 

 

"I am confused. 
I don't understand the buffers from 3oz-7oz which is right?
I don't understand the tube length issue and the spring. Does it need a longer or stronger spring?.
I'm assuming the normal buffer for a 308 is a longer tube and longer buffer and maybe heavier buffer.
It looks like possibly you are able to use a standard length mil spec tube on it IF you use a special spring and short and heavy buffer?? help

 

 

Welcome to the forum maybe try starting your own thread to help with your questions also feel free to post up in the intro area

[survivalshop]

16 hours ago, xxlfitness@yahoo.com said:

Im new to this forum and 308/7.62. I have lots of experience with AR .556 platforms. I need some help building my first 308 AR.

I read this thread and have some questions. there is much talk of different brands, when piecing one togther from scratch, how

do

you know what info applies to my build? Mine is a carbine length as far as the gas system. But you guys are referring to the stock and tube in terms of carbine vs rifle use also and I'm confused by that. My lower is a basic PSA-10 and the upper is a DPMS LR 308 Oracle A3.

The only thing I am lacking finishing it is the buffer/stock spring assembly.

Here is something below that I posted sometime back and never got an answer:

 

 

"I am confused. 
I don't understand the buffers from 3oz-7oz which is right?
I don't understand the tube length issue and the spring. Does it need a longer or stronger spring?.
I'm assuming the normal buffer for a 308 is a longer tube and longer buffer and maybe heavier buffer.
It looks like possibly you are able to use a standard length mil spec tube on it IF you use a special spring and short and heavy buffer?? help

 

 

   


   Yes the 308AR builds can get a little confusing . all depends on a few factors & because of no MilSpec standards of 308AR's , some manufacturers of Lower Receivers make it more difficult because they make their's proprietary in some ways . The PSA 10 has seen some issues in this area .

  Basically stick to one or the other Systems , be it Armalite's AR 10 systems , as in mrraley's description in his post above or the DPMS system . Basically the AR 10 uses a AR 15/M4/M16 Buffer ( normally a HB ) with AR 10 Receiver Extension ( Buffer Tube ) & AR 10 Buffer Spring . The DPMS system uses a STD AR 15/M4/M16 Receiver Extension , DPMS LR 308 Buffer & Spring . Just keep the correct system for Collapsible stock or Rifle Stock system.

  Your Carbine Gas system has little to do with it , though you can tweak the system with a Heavier Buffer or Spring & or a Adj. Gas Block . In 308 , the Carbine Gas system will be the most violent in terms of felt recoil, so some use the Tweaking methods as I described .

 Its not just like throwing parts together as in an AR 15,some may need special attention to be completely reliable . If I were you I would look around the PSA 10 threads on this Forum to see what has been done to them . 

 
  
  

[xxlfitness@yahoo.com]

Ok thanks so much. BUT. Now that i have this PSA, what stock,tube. And buffer do i need to use for the best chance of it working

[survivalshop]

 I would try AR 10 ( Armalite ) components or configuration buffer system , its a little longer & may be a little more forgiving if needed . Collapsible or Rifle , any stock will fit both systems ( DPMS type or AR 10 ).

  Be careful , look at the spec's in mrraley's Post above .

 I ordered a 308AR DPMS type , rifle Buffer Spring last year for my 18" build & got a AR 15 rifle spring & I used it & didn't check it . Found it out when comparing springs in one of my 308 AR's for a thread here . I trusted a well known company to send the correct part ( people make mistakes )& I took it for granted , my bad & I should known better . So many here have used or were supplied with wrong components & had function issues. 

  Or try the DPMS system , your choice , just make sure you match the correct components .

[Frankh252]

Since it's a DPMS Oracle (I have one too) I'd just go with a DPMS setup. They have mil-spec & commercial sizes & either of them should work just fine.

http://www.brownells.com/rifle-parts/receiver-parts/buffer-tube-parts/buffer-tubes/ar-style-308-stock-mounting-kits-prod44751.aspx

[mekkisman]

I have just built a PA-10 using their lower and 18" mid length kit. I would like to install an M16A1 butt stock. The M16A1 buffer tube is about 2" deeper inside than the supplied carbine buffer tube. Is there any reason I can't just install a 2" spacer to fit between the back of the tube and the spring? I'm a retired machinist with access to a lathe and aluminum and Delrin stock.

[jtallen83]

I don't think the carbine tube has the threaded end to receive the screw, unless PSA has some proprietary stuff going on. For the money why not just buy the right tube? They are cheap relatively speaking.

[Matt.Cross]

21 minutes ago, jtallen83 said:

I don't think the carbine tube has the threaded end to receive the screw, unless PSA has some proprietary stuff going on. For the money why not just buy the right tube? They are cheap relatively speaking.

I think you misunderstood the question. If I'm reading correctly, he wants to use a spacer inside the full-length buffer tube and use his carbine buffer and spring.

[jtallen83]

44 minutes ago, Matt.Cross said:

I think you misunderstood the question. If I'm reading correctly, he wants to use a spacer inside the full-length buffer tube and use his carbine buffer and spring.

Need to drink my coffee before posting...........

[98Z5V]

14 hours ago, mekkisman said:

 Is there any reason I can't just install a 2" spacer to fit between the back of the tube and the spring? I'm a retired machinist with access to a lathe and aluminum and Delrin stock.

There is no reason at all that this would not work.  It will.  Just make accurate measurements on both systems, or the internal depth.  Correct spacer length will equal the difference between the two internal depths.  Diameter of the material should be 1".  You can make it tight fit if you want, and take the diameter up a little. You can always punch the spacer out from the end, if you needed to remove it.

Edited June 27, 2017 by 98Z5V