AR10/.308 AR Build knowledge thread.

[daddyusmaximus]

So I ordered an Aero Precision .308 upper for my SBR build. Then went web surfing and found a good deal on mags I thought I'd let people know.


Brownells .308 AR mags on sale. $11.99 down from $19.99. I ordered 10. Reviews were mixed, but for 12 bucks a pop, I took a gamble. I've had good luck with their 5.56 mags.

http://www.brownells.com/magazines/r...prod71942.aspx

[LRRPF52]

The Vltor A5 tube works on AR10s and LR-308s with an AR15 carbine buffer length, preferably one of the heavier buffers like an H3.

The problems I'm seeing are that even when people assemble all the "correct" parts for the buffer/recoil system, we are still seeing impact from the carrier rails on the receiver extension threads at the bottom lead edge of the lower receiver right around the buffer retainer area.

You can mitigate this with washers inside the extension tube, or notching your extension tube to allow another turn or two to locate the buffer bumper collision more forward, but all of this is a result of after-market parts that were never designed and tested by the same team of competent engineers under one roof.

[daddyusmaximus]

The Vltor A5 tube works on AR10s and LR-308s with an AR15 carbine buffer length, preferably one of the heavier buffers like an H3.

The problems I'm seeing are that even when people assemble all the "correct" parts for the buffer/recoil system, we are still seeing impact from the carrier rails on the receiver extension threads at the bottom lead edge of the lower receiver right around the buffer retainer area.

You can mitigate this with washers inside the extension tube, or notching your extension tube to allow another turn or two to locate the buffer bumper collision more forward, but all of this is a result of after-market parts that were never designed and tested by the same team of competent engineers under one roof.

First time I've read this. Good to know what to look for.

[polydeuces]

Is there anyone running the A5 system on a .308 AR? I'm building one on a CMMG lower (DPMS pattern) with an Aero Precision upper. I found out that they make .308 A5 buffer tubes, but no internal parts, and no complete kits.

Tube: https://www.vltor.com/shop/a5-system...ver-extension/

It says the following:

"If you are using this for a DPMS rifle, you will need to call DPMS for the correct parts needed. Attempting to use this tube with parts other than these, will result in damage to your rifle."

So I get on the DPMS site, and they don't list any parts for a fixed stock .308. It was my understanding that the A5 system uses a rifle length spring and special buffer. Now what?

This is for a SBR that will use a 12.5" Rainier Arms UltraMatch .308 Barrel. https://www.rainierarms.com/rainier-...-armalite-dpms

Please see post #146 and post #59, pg. 6

[daddyusmaximus]

OK, Guess I could have looked better first...

[CoryCop25]

COMPREHENSIVE RECAP.



The VLTOR A5 system:
If a carbine type stock is preferred over a rifle (A2) RE one of THE best options hands down is the VLTOR RE10/A5 RE's.
This can be run with a rifle spring/H3 buffer, as well as the A5 set-up.

OK I'm a little confused....
I am almost finished with my 308 build. I have everything but the BCG and iron sights...
I have the RE10 on my lower. I have a pile of AR-15 Carbine buffers and a pile of A5 buffers.....
If I decided to use an A5 buffer in my RE10, what spring do I use? Ar-15 rifle or 308 rifle?

[MistWolf]

OK I'm a little confused....
I am almost finished with my 308 build. I have everything but the BCG and iron sights...
I have the RE10 on my lower. I have a pile of AR-15 Carbine buffers and a pile of A5 buffers.....
If I decided to use an A5 buffer in my RE10, what spring do I use? Ar-15 rifle or 308 rifle?

When using an A5 style RE on a 308 AR, you MUST use carbine type buffers. The carrier of the 308 AR is longer. If you use the A5 type buffer, it will be too long and the carrier prevented from going all the way to the rear. In fact, the A5 type RE was developed by Armalite so an adjustable carbine stock could be used while allowing parts commonality with carbine buffers.

You'll have too play with action springs to see whether a rifle or carbine spring works best. I believe my Big Smith came with a carbine spring. If you use a standard rifle spring, it's possible the coils will come into contact with each other under full compression on a carbine buffer. A Tubbs flat spring will let you run a full length spring without coil contact and I've run one successfully in the Big Smith

[polydeuces]

Apologies for the omission

The VLTOR RE10/A5 RE uses a standard AR15 buffer. Let me get back on weight.
A Sprinco orange so far has been smooth and reliable.

But there are many other options.

[polydeuces]

Update for those looking at shooting suppressed:
Matching same lower with 13.5" barreled upper, adjustable gas block dialed in for federal (dialing without can) then shoot suppressed runs without a hick-up.
Very smooth and no doubt could be tweaked even more.

[FaxonNathan]

my first light weight AR 308 weighed 7.7 pounds using a Faxon 18 inch 36.1 ounce barrel. My last used the Juggernaut 18 inch fluted 5R barrel @ 33.8 ounces. And for all you that say what about the recoil, I already have it shooting soft and accurate.

I should get my 2A Xanthos receiver set late next week, have all the other build parts ready to go. Will reuse the Juggernaut 18 inch until my 16 inch X-Caliber fluted 308 barrel is finished, hoping for less than 31.8 ounces. Every part has been tested and works. The barrel is giving sub half inch groups with both Mk319 130 SOST and with FGM 175 SMKs.

The goal is under 4.5 pounds using DPMS Gen 1 AR 308 pattern parts.

My last AR308 got down to 4.99 pounds by 1/5/2016 using the 23 ounce receiver set from Tactical Machining.
The Xanthos receiver set weighs 16.3 ounces so an immediate 6.4 ounces cut.
Also latest CF hand guard is 0.2 ounces less and hoping the next pistol grip will cut between 0.5 to 0.7 ounces.

Upper Parts:
2A Armament Xanthos Upper receiver 7075 T6 9.00 ounces
Juggernaut Tactical Arms 18 inch fluted barrel @ 33.8 ounces
2A titanium gas block @ 0.60 ounces
Gas tube mid length @ 0.80 ounces
titanium muzzle brake @ 0.67 ounces
Clark Custom Aluminum barrel nut @ 1.18 ounces
AR 308 carbon fiber hand guard 1.60 ounces in mid length 10.5 inches
Toolcraft Titanium 308 BCG @ 11.80 ounces with ti firing pin
Charging handle @ 1.15 ounces



Lower Parts: Total weight ~ 18 ounces

2A Armament Xanthos lower @ 7.30 ounces
Mag Pul K grip @ 1.7 ounces
V7 titanium grip screw 0.113 ounces
V7 Mag catch aluminum 0.173 ounces
V7 Aluminum/titanium selector 90 degree 0.293 ounces
V7 aluminum AR 308 takedown pins 0.26 ounces
V7 tool steel bolt catch 0.31 ounces
Smoke Composite stock 3.3 oz.
AR308 carbine buffer (no weights) 0.85 oz.
NF polymer trigger group 0.65 oz with titanium trigger pins
DPMS carbine buffer spring @ 1.5 ounces
Titanium buffer retainer, mag catch plunger

Sweet build. Might I recommend you take a look at 2A's .308 pencil barrel. Should easily meet requirements and take you near 4 lbs!