Guidance building my 1 and only 308 AR

Robocop1051 · October 11, 2014

With 7.62x39 ammo selling at .2 to .25 per round... I can't see why more people aren't building into this caliber?

My next build is almost finished. Just waiting on some machine time to fix/fabricate a new part.

FaRKle! · October 12, 2014

Farkle! you said the following:

For the buffer system go with a VLTOR A5 receiver extension (6 or 7 position depending on the stock you get), AR-10 action spring, and AR-15 H3 buffer.
The gas block and gas tube are the same as AR-15 parts. The LPK you get will need to be LR308 compatible (enlarged bolt catch and larger mag release).

I will get a mil-spec STR stock per above. Any more direction these items? You mention 6 or 7 positition VLTOR A5 receiver extension (6 or 7 position). Which way do I go on this? Is there a good quality gas block, gas tube and LPK you can recommend? I honestly know jack squat about who makes good stuff on these.

At the time I didn't know which stock you were getting. Since you're getting the STR, get the 7-position receiver extension since the STR is long enough to close all the way on it (some other stocks like the CTR aren't long enough to close all the way and thus would need the 6-position model).

If you want an adjustable gas block (ever plan on running suppressed?) I'd go with the SLR Sentry, otherwise, a BCM or Geissele one works great. Gas tubes are pretty standard. Any well known brand or store's should work. For your 16" barrel it'll probably be mid-length.

Bang4Buck · October 12, 2014

Well I just took the first step and went ahead and ordered the Mega Arms Maten Keymod Extended rifle set. I have not seen a single negative review on it so I feel like that is a safe starting point.

Looks like the LPKs all come with a grip, even when you leave out the trigger (which I will do since buying SSA or SSA-E). Guess I'll pick one and try that grip before upgrading.

Edited October 12, 2014 by Bang4Buck

edgecrusher · October 12, 2014

Wait till you get it, it'll be Mega for life. I love their stuff.

Bang4Buck · October 13, 2014

Follow up questions:

1 - Is there any functional difference between these 2 buffer tubes, other than the manufacturer? Found it odd the Colt was selling but not he vltor

http://www.midwayusa.com/find?userSearchQuery=h3+buffer

2 - Is this the exact spring you would recommend: http://www.armalite.com/ItemForm.aspx?item=EA1095

3 - Looks like this is the receiver extension: http://www.midwayusa.com/product/348370/vltor-a5-recoil-system-carbine-receiver-extension-buffer-tube-7-position-mil-spec-diameter-ar-15-aluminum-black

If those are all correct, my biggest decision will revolve around which barrel to get as well as choosing BCG. The fact there is no mil-spec/standard makes it tougher for a noob like me to know which way to go. I already know tirgger, stock, grip, etc... so I'm in good shape on the rest.

FaRKle! · October 13, 2014

Follow up questions:

1 - Is there any functional difference between these 2 buffer tubes, other than the manufacturer? Found it odd the Colt was selling but not he vltor
http://www.midwayusa.com/find?userSearchQuery=h3+buffer

DO NOT get the A5 buffer. That buffer is too long and is only meant for AR-15 A5 systems. I usually get my buffers from Damage Industries because they run sales so often.

2 - Is this the exact spring you would recommend: http://www.armalite.com/ItemForm.aspx?item=EA1095

Yes. It may be available other places too (Heavy Buffers also sells them).

3 - Looks like this is the receiver extension: http://www.midwayusa.com/product/348370/vltor-a5-recoil-system-carbine-receiver-extension-buffer-tube-7-position-mil-spec-diameter-ar-15-aluminum-black

Correct, that's the right receiver extension.

Edited October 13, 2014 by FaRKle!

98Z5V · October 14, 2014

Like Fark stated, you can't run that VLTOR A5 buffer, man.

Bang4Buck · October 15, 2014

Look at what I just got? Ain't she purdy? :banana:

The .308 AR build journey has officially begun.

Robocop1051 · October 15, 2014

I have to admit. There are VERY few that can rival the quality and beauty of a matched MEGA set.

Great looking set

edgecrusher · October 15, 2014

And surprisingly light too! Congrats

Bang4Buck · October 15, 2014

Thanks. I'll keep you guys posted on the build.

My most critical decision will be around which 16 inch barrel and BCG to go with. Any suggestions are welcome

EasyEJL · October 15, 2014

if budget were no issue.... probably a proof carbon fiber

http://proofresearch.com/the-products/barrels/ar-carbon-fiber-barrel-calibers-lengths/

Bang4Buck · October 15, 2014

if budget were no issue.... probably a proof carbon fiber
http://proofresearch.com/the-products/barrels/ar-carbon-fiber-barrel-calibers-lengths/

Budget is an issue. I'm think 300, maybe 400 max for a barrel.

Leaning towards this https://www.rainierarms.com/?page=shop/detail&product_id=3459

or maybe a mega barrel of comparable price

edgecrusher · October 15, 2014

Nothing wrong at all with that Rainier, and if you buy a bolt at the same time they headspace!

Robocop1051 · October 15, 2014

Nemo makes a nice melonite barrel.

washguy · October 15, 2014

Bang the magpul acs stocks in mil spec work for me....they lockup well..no wiggle.... the 308 car buffer/spring have always worked for me too....on the charging handle get one with a big latch ,so it works with a scope....all of my 308's use Rainier barrels except one....16 " is the ticket with an apex handguard :) Wash

Bang4Buck · October 16, 2014

Bang the magpul acs stocks in mil spec work for me....they lockup well..no wiggle.... the 308 car buffer/spring have always worked for me too....on the charging handle get one with a big latch ,so it works with a scope....all of my 308's use Rainier barrels except one....16 " is the ticket with an apex handguard :) Wash

I am leaning towards STR stock right now as I have it on colt 6920 and I like the cheek weld and friction lock.

Edited October 16, 2014 by Bang4Buck

Bang4Buck · October 16, 2014

I am leaning toward the armalite BCG. I assume any gunsmith can head space if I buy the barrel from someone else?

FaRKle! · October 16, 2014

I don't believe Armalite bolts and LR308 barrel extensions are compatible.

Bang4Buck · October 16, 2014

I don't believe Armalite bolts and LR308 barrel extensions are compatible.

I was going based on this: http://308ar.com/carriers.htm

Sounds like if I get the entire BCG I am ok?

Edited October 16, 2014 by Bang4Buck

edgecrusher · October 16, 2014

Bang, you are ok. As long as you order the barrel in Armalite pattern. I don't think he saw you are choosing the Armalite pattern for this build. He was just making sure you didn't mix and match.

My MaTen build is going to be put together similarly but I'm using a Noveske barrel/ Armalite bcg.

Bang4Buck · October 16, 2014

Bang, you are ok. As long as you order the barrel in Armalite pattern. I don't think he saw you are choosing the Armalite pattern for this build. He was just making sure you didn't mix and match.
My MaTen build is going to be put together similarly but I'm using a Noveske barrel/ Armalite bcg.

I am slightly confused now. I thought what I was doing was the DPMS pattern, since I'm told my LPK will need to follow DPMS/LR308. I guess that means the upper will have an Armalite pattern if I use their BCG? And once I headspace I need to stick with same BCG/Barrel pattern going forward. This would be soooooooo much easier if there was a standard pattern in the 308 world. 5.56 was much easier to learn!

edgecrusher · October 16, 2014

Slow down cowboy.... The beautiful thing about the MaTen is you can do either pattern. Here's the thing:

The barrel and bolt need to match. The barrel you showed us above from Rainier is available in Armalite pattern, so with the Armalite bcg you can headspace and be all set. You cannot however headspace an Armalite bolt to a DPMS barrel, square peg to round hole. If you do get the DPMS pattern, you'll need a different bcg.

Your parts kit should be fine, if anything it'll just be the catch, which can be ordered from Armalite separately and is a beefier better part, but you may not need it.

Bang4Buck · October 16, 2014

Slow down cowboy.... The beautiful thing about the MaTen is you can do either pattern. Here's the thing:
The barrel and bolt need to match. The barrel you showed us above from Rainier is available in Armalite pattern, so with the Armalite bcg you can headspace and be all set. You cannot however headspace an Armalite bolt to a DPMS barrel, square peg to round hole. If you do get the DPMS pattern, you'll need a different bcg.
Your parts kit should be fine, if anything it'll just be the catch, which can be ordered from Armalite separately and is a beefier better part, but you may not need it.

That makes sense. I didn't see anything in the barrel description to indicate which pattern was followed. The Mega barrel I looked at specified dpms pattern barrel extension

Edited October 16, 2014 by Bang4Buck

Bang4Buck · October 17, 2014

Just got an e-mail from the gunsmith I am going to work with on putting everything together. Here is what he said. Let me know your thoughts:

Just got off the phone with DPMS. They said the armalite BCG is a different design from the DPMS design and would not work. They could not speak for the Aero Precision. I sent Aero an email since they didn't list a phone number to call. DPMS also said that the length difference on the ar15 H3 buffer compared to the 308 buffer would cause cycling problems.

For a gas block I would suggest the YHM clamp style gas block. Clamp style as opposed to the set screw gives a tighter seal around your gas port. Either clamp style or set screw would be fine though.

Any castle nut will work, nothing special to get here.

any thoughts on what he said?