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Buffer tube and weight question


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#1 RoadW3

 
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Posted 20 December 2011 - 03:46 PM

I looked and didnt find exactly what I was looking for so I thought I would toss the idea out there.  Thanks for any help.

I am buying the parts now to do my Mega build and I only want to buy parts one time.

I am wanting to use a Mil Spec carbine buffer tube on the build for stock selection and to keep me from buying a bunch of parts for only one rifle.  I was reading the H3 buffer could be used with the armalite spring.  But on Mega's website they recomend a buffer that is almost 100 bucks and it doesnt say if it is for Mil Spec of commericial peices.  Can someone clear this up for me please on what buffer and spring I should buy for the Mil Spec tube.

Thanks,
Eric 

#2 washguy

 
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Posted 20 December 2011 - 04:33 PM

Hi Eric  Ive got two carbine mega builds that im using the dpms style barrel/bcg...if you are doing that....then just a mil spec tube,308 carbine spring and 308 buffer...nothing fancy...no flat wire spring or h2 h3 buffer...i tried those  combos and they prevented lockback.....but if you are going the armalite route with barrel/bcg someone else will have to chime in thats using  the armalite  barrel/bcg.  Wash

#3 survivalshop

 
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Posted 20 December 2011 - 04:34 PM

The internal dia. of all receiver extensions are the same ,be it commercial or milspec. The buffers are all the same dia. , so will fit any receiver extension .

Are you building a 308 platform rifle ?

There are those that use 5.56 buffers for 308 rifles , but the Armilite receiver extensions are ,I think, longer then M16/AR15 /DPMS 308 type extensions ( some one correct me if its the other way around )

I have Superior Shooting systems springs for my 308's & they work with both collapsible or std stock systems.

If you want to use the Armilite system , get an Armilite receiver extension also & you can use the components you describe.

I use 308 designated components in my 308's & I don't have to tweak a thing. Same receiver extensions as an M16/AR 15, be it commercial or Mil spec.

I think those $ 100 buffers are over rated, but may be needed if not using matched components.

#4 Robocop1051

 
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Posted 20 December 2011 - 05:52 PM

SS, you're right about the longer extensions from Armalite. Although I think it's just the full length extension that's longer. The carbine/collapsable extensions should be the same as others.

@RoadW3 / Eric,
You can't pick a buffer too short, but you can pick one that's too long. Any carbine or shorty buffer will fit in your rifle. I read somewhere that the 5.56 H3 weighs the same as the 308 standard buffers.

If money is available, the Enidine "AR-Restor" hydraulic buffer is also an option. More expensive than most, but still under $100

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#5 RoadW3

 
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Posted 20 December 2011 - 11:06 PM

Sorry I just reread my original post and I know I was talking about the mil spec tube but I was meaning the length cause I know that some of the buffer tubes are longer. I am going to be running a carbine length AR-15 tube. I just picked up the dpms 308 buffer and spring. I am using a dpms bolt carrier, bolt, and SASS barrel. I know it's heavy but rainier didn't have the select barrel in stock and with an expected arrival in late Jan to feb I didn't want to wait that long.

Thanks again for the help,
Eric

#6 98Z5V

 
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Posted 21 December 2011 - 04:11 AM

ALL carbine buffers are the same length, be it AR-15 or .308 AR (RRA stuff doesn't count...).  AR-15 carbine H3 buffers are direct swaps for Armalite AR-10 carbine buffers - size and weight identical.  DPMS LR-308 carbine buffers are lighter, and will benefit from running the heavier Armalite component, or an AR-15 H3 carbine buffer.

ALL Rock River .308 stuff is different.

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#7 Slash

 
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Posted 27 December 2011 - 10:47 PM

I'm going to try to correct/clarify some inaccurate info in this thread.

First, as was stated previously, ALL buffer tube have the same inside diameter. Only the outside diameter is different. Buffer selection is dependent on the length of the tube (and the type of gun), not the diameter.

Carbine buffer tubes (receiver extensions) are available in two different lengths.  A standard AR15 type tube is 7" long inside and an AR10 (VLTOR) tube is 7-3/4" long inside. 

All carbine buffers ARE NOT the same length!  There are three basic variations. 
1 - AR15 buffers are 3.250" long and will work (obviously) in any AR15 with a standard carbine buffer tube.  These same buffers will also work on ArmaLite and DPMS pattern .308 ARs if you use the extended buffer tube. 
2 - .308 carbine buffers are shorter and will allow you to use an AR15 type buffer tube on a .308 AR.  A modified .308 spring is sometimes required for proper function.
3 - Rock River Arms require an even shorter buffer and a modified spring.

It is important to note that you should never use a buffer that is shorter than required for your specific application.  You most definitely CAN pick a buffer that it too short. IE - A RRA .308 carbine buffer will physically fit into any other configuration.  But if you were to install one of these buffers into say, an AR10 with an AR15 tube, the bolt will over-travel and the carrier key will strike the lower receiver ring and mayhem will ensue.

Is is important to make sure that you use a .308 buffer spring in ALL .308 ARs.  NEVER use ANY AR15 buffer spring in a .308 AR.  I strongly recommend using ArmaLite AR10 buffer springs, and I discourage the use of any 'Flat Wire' spring.

The difference between a "$100 buffer" and the DPMS .308 carbine buffers is MASS.  The DPMS buffers weigh only about 1/3 oz. more than and AR15 carbine buffer. Way too light when you consider the differences in pressure between .223 and .308. DPMS merely took a shortcut, there's a reason why they don't offer a lifetime warranty.  Their buffer is simply an H3 buffer that is cut down in length and then they remove one of the Tungsten weights.  A great 'field expedient' method, but not good for your gun in the long term.  A lot of customers turn to me when their DPMS factory carbines start breaking parts. I strongly discourage using any buffer lighter than an H3 in a .308 AR.

Final note - You can't 'upgrade' a factory DPMS carbine to an H3 buffer unless you also upgrade to an ArmaLite/VLTOR buffer tube.  The DPMS tube is too short and will restrict bolt travel.  The gun will not eject/chamber a round from the magazine.

I hope that this information is helpful.  If any questions remain please feel free to contact me.


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#8 edgecrusher

 
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Posted 27 December 2011 - 10:52 PM

thanks for the solid info and welcome to the site. great contribution
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#9 98Z5V

 
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Posted 27 December 2011 - 11:24 PM

We've needed you here for awhile, Slash - glad you showed up.  <thumbsup>

I like the Woody Hayes avatar better, man.  ;D

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#10 Slash

 
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Posted 27 December 2011 - 11:41 PM

I honestly wasn't aware of this forum until today.  So many forums, so little time.

I updated the avatar.  ;)
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#11 98Z5V

 
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Posted 27 December 2011 - 11:54 PM

I updated the avatar.  ;)


Haha!  Awesome!  <thumbsup> ;D

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#12 Rsquared

 
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Posted 29 December 2011 - 03:31 AM

I use one of the heavy buffers that I got from slash for one of my Armalite carbines. It functions great. Reduced recoil (not that it was an issue). Between that and the JP adjustable gas block, the carbine runs great with the AAC suppressor.

Ron

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#13 cyclops

 
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Posted 08 December 2012 - 06:26 PM

I'm sorry to resurrect this thread, but I have an issue that i'm wondering if it can be fixed with a tweak of my tube, buffer sizes.  I have DPMS patterned IRA lower reciever with a DPMS BCG, DPMS upper receiver, DPMS .308 receiver extension, buffer and spring and 18.5" Criterion Barrel with rifle length gas system appears to be "under gassed".  When firing M118LR, M118SB, M80 ball and 150 gr. Rem Core Lokt it ejects but will not strip new round from Magpul mags and will not lock to rear on last round on any of my mags.  This leads me to believe it's under-gassed.  I've checked the carrier key and it's tight, i've checked the gas port hole and gas block, they're lined up, and there is no wear on my carrier that would indicate that it's getting hung up.  I lube my BCG VERY well prior to shooting. 

Does anyone have any ideas as to how I can fix my issue?  Will the longer Armalite tube and H3 buffer help or since this seems to be a fix for over-gassed guns do you think it will make things worse?  I'm thoroughly confused.
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#14 Robocop1051

 
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Posted 08 December 2012 - 06:48 PM

You can try the JP LMOS system. That usually requires an adjustable gas block, LMOS carrier and LMOS buffer.

You can also try using a Tubb Chrome Silicone Flat Spring. This is probably the cheaper of the two choices.

Having Tom and I post on the same thread is like having two fat chics at a night club. It doesn't matter what song is playing, we are going to take over the dance floor.


#15 imschur

 
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Posted 08 December 2012 - 07:03 PM

Is this a new build? Will it lock and feed when you cycle manually? Do you have a friends that you can do a upper lower swap with?

#16 Slash

 
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Posted 08 December 2012 - 07:39 PM

I don't recommend using a lightweight carrier or flat wire spring. Both of these products can lead to other problems. 

Can you manually lock the bolt back?
How long is your buffer?
How many coils on your buffer spring?
Is your gas tube properly installed in the gas block and obstruction-free?
Have you looked at the gas rings on your bolt?
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#17 cyclops

 
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Posted 08 December 2012 - 08:02 PM

This is a new build.

I just checked my rifle and no my bolt will not stay locked back unless there is a mag in it...never checked this before, interesting

My gas port and block are obstruction free and align just fine.

I looked at the gas rings and they are all in apparently good condition.

My buffer is the shorter 3 oz DPMS .308 buffer and the spring is the .308 spring with what appears to be 28 or 29 coils. 

BTW Slash, I'm the guy who sent you an e-mail earlier today reference the same issue.
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#18 imschur

 
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Posted 08 December 2012 - 08:08 PM

This is a new build.

I just checked my rifle and no my bolt will not stay locked back unless there is a mag in it...never checked this before, interesting



Well the follower actuates the latch for the bolt lock. You can test it with an empty mag.

My concern is the IRA portion of the equation. We have a few threads with IRA issues.

#19 cyclops

 
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Posted 08 December 2012 - 08:24 PM

I was mistaken, bolt will lock to the rear manually with and without a magazine either empty or with a rounds in it.

I too am concerned about the IRA lower, I've read the threads on them also but I can't see how it would translate to the issue of an under gassed rifle?
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#20 Robocop1051

 
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Posted 08 December 2012 - 08:44 PM

Slash is by FAR the most knowledgeable on buffer issues. If it's a buffer issue he'll be the guy with the answers.

Is it possible that your parts are still too rough and causing friction? I used some 0000 steel wool to smooth out the inside of one of my upper receivers. I wrapped the tip of my power drill and spun it for a min or two. It made everything much smoother. Also, what oil are you using? How much of it did you use?

What hammer spring are you using?

Having Tom and I post on the same thread is like having two fat chics at a night club. It doesn't matter what song is playing, we are going to take over the dance floor.





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