Guidance building my 1 and only 308 AR

FaRKle! · 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.

As we said before, it all depends on which barrel extension is being used. If you get a DPMS LR308 pattern barrel extension, then you need a LR308 pattern BCG. If you get an Armalite AR-10 pattern barrel extension, then you need an AR-10 pattern BCG. Aero Precision parts are made in LR308 pattern.

DPMS also said that the length difference on the ar15 H3 buffer compared to the 308 buffer would cause cycling problems.

What DPMS said applies to a DPMS pattern buffer system. I specifically recommended an AR-10 buffer system because it'll let you tune it more easily and has more margin with regards to reliability. Yes, you can use an AR-10 buffer system on an LR308 pattern gun. My PWS is an example. You won't into buffer length issues because the receiver extension you'll be using (VLTOR A5) is longer than the usual AR-15 carbine receiver extension.

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.

There's a reason no military rifles use clamp on blocks. Set screw plus dimple is more mechanically secure. Clamp on blocks rely on a screw that has a lot of strength across the diameter of the screw (the shortest dimension!) since when tightening it's effectively bending the screw. With a set screw block the force is only concentrated on the threads of the screw (most surface area). If the barrel is dimpled, then you can't physically rotate the block while a clamp on block can still rotate.

Also, Damage Industries is having a 25% off sale with code "TRICKORTREAT". Time to get your buffer.

Edited October 17, 2014 by FaRKle!

Bang4Buck · October 17, 2014

As we said before, it all depends on which barrel extension is being used. If you get a DPMS LR308 pattern barrel extension, then you need a LR308 pattern BCG. If you get an Armalite AR-10 pattern barrel extension, then you need an AR-10 pattern BCG. Aero Precision parts are made in LR308 pattern.

What DPMS said applies to a DPMS pattern buffer system. I specifically recommended an AR-10 buffer system because it'll let you tune it more easily and has more margin with regards to reliability. Yes, you can use an AR-10 buffer system on an LR308 pattern gun. My PWS is an example. You won't into buffer length issues because the receiver extension you'll be using (VLTOR A5) is longer than the usual AR-15 carbine receiver extension.

There's a reason no military rifles use clamp on blocks. Set screw plus dimple is more mechanically secure. Clamp on blocks rely on a screw that has a lot of strength across the diameter of the screw (the shortest dimension!) since when tightening it's effectively bending the screw. With a set screw block the force is only concentrated on the threads of the screw (most surface area). If the barrel is dimpled, then you can't physically rotate the block while a clamp on block can still rotate.
Also, Damage Industries is having a 25% off sale with code "TRICKORTREAT". Time to get your buffer.

Would this BCM block work well? http://www.bravocompanyusa.com/BCM-Low-Profile-Gas-Block-p/bcm-lgb-.750.htm

barrel is .750 so that would match

waiting to hear back from my guy on your buffer system comments, but I believe you. He may not have realized that VLTOR was longer than a normal m4

washguy · October 17, 2014

Bang you said

"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"

On the Rainier site....they offer some barrels with a choice of extensions and some only DPMS style....their match and ultra match and Noveske offer the choice...the selects only DPMS... :) Wash

edgecrusher · October 17, 2014

On the Rainier site....they offer some barrels with a choice of extensions and some only DPMS style....their match and ultra match and Noveske offer the choice...the selects only DPMS... :) Wash

Noveske only comes in Armalite, that's what I'm doing with the sbr.

FaRKle! · October 17, 2014

Would this BCM block work well? http://www.bravocompanyusa.com/BCM-Low-Profile-Gas-Block-p/bcm-lgb-.750.htm

barrel is .750 so that would match

waiting to hear back from my guy on your buffer system comments, but I believe you. He may not have realized that VLTOR was longer than a normal m4

Yes, the BCM block will work great (it has very tight tolerances).

If you ask the DPMS rep again about the buffer system, you'll need to specify that you're using a VLTOR A5 receiver extension and not their normal carbine receiver extension. The A5 extension is the same length as an AR-10 extension.

Bang4Buck · November 23, 2014

OP circling back on the final build. Thanks to everyone for their help. Here is the complete parts list I went with:

1 - MEGA ARMS MKM MATEN Keymod Upper / Lower Set - http://www.capitolarmory.com/mega-arms-mkm-maten-keymod-upper-lower-set.html

I got this on sale for $720 including tax and shipping. And that was the extended rifle length set which is 14 inches. Also included 9 slot rail and charging handle.

2 - H3 Buffer and castle nut through Damage Industries - $40 including shipping and tax during Halloween sale

3 - Geissele Super Semi-Automatic Enhanced (SSA-E) - on sale for $194 through Trading Place Pawn. Price included shipping and no tax.

4 - DPMS LPK minus FCG - http://www.brownells.com/rifle-parts/receiver-parts/parts-kits/308-lower-parts-kit-minus-fire-control-components-sku231000334-27207-111705.aspx

Got it for $50

5 - A5 receiver extension - http://www.brownells.com/rifle-parts/receiver-parts/buffer-tube-parts/buffer-tubes/a5-receiver-extension-sku100010797-55056-111100.aspx

Paid $47.50

6 - STR stock - http://www.brownells.com/rifle-parts/stock-parts/buttstocks/str-mil-spec-stock-black-sku100009321-45226-102656.aspx

paid $76

7 - Noveske QD end plate http://www.brownells.com/shooting-accessories/slings-sling-swivels/tactical-sling-mounts/qd-receiver-end-plate-sku100004756-31766-57871.aspx

cost $27

8 - Magpul MIAD 1.1 grip http://grabagun.com/magpul-mag520-blk-miad-gen-1-1-grip.html

paid $28

9 - BCM Low Profile Gas Block (steel with set screws) 750 cost $45

10 - BCM mid length gas tube $13

11 - Larue Tactical A2 flash hider for 308 - $20

12 - Aero Precision 308 complete BCG(follows DPMS pattern) http://aeroprecisionusa.com/aspx/store/productdetail.aspx?pid=175

cost $195

13 - Rainier Arms 308 Match 16 inch Barrel DPMS pattern https://www.rainierarms.com/rainier-arms-matchtm-308-barrel-21

cost $315

FYI if you buy a barrel from Rainier, you don't have to buy the BCG through them to get free headspacing. Call and they'll tell you how to add this to your order

14 - AR 10 buffer spring - $10

That got me to right at $1,750 for the base setup I want for way less than the LMT, Larue, or FN. I could have gone much cheaper in a few area to keep the cost down such as going with Aero Precision receiver set, use the trigger and grip that comes with the DPMS LPK, Rainier Select barrel instead of Match barrel, etc... That would have probably saved several hundred bucks, but I would not have been as happy. My pictures don't do it justice. This is a great looking setup and I'm excited to go break it in soon.

I will likely do a few other things, such as Raptor, BCM, or Mecharmor TacOps1 charging handle (would be interested to hear you opinions on which is better), a good light never hurts, etc.... But I have the foundation I want and I'm quite certain I'll save money vs. the LMT, Larue, or FN routes.

unforgiven · November 23, 2014

Very nice, good job brother and the cost breakdown was excellent. <thumbsup>

Christopher67 · November 26, 2014

I went with this rail https://www.odinworks.com/308_KMod_Forends_p/f-15-km-308.htm

Christopher67 · November 26, 2014

OP circling back on the final build. Thanks to everyone for their help. Here is the complete parts list I went with:
1 - MEGA ARMS MKM MATEN Keymod Upper / Lower Set - http://www.capitolarmory.com/mega-arms-mkm-maten-keymod-upper-lower-set.html

I got this on sale for $720 including tax and shipping. And that was the extended rifle length set which is 14 inches. Also included 9 slot rail and charging handle.
2 - H3 Buffer and castle nut through Damage Industries - $40 including shipping and tax during Halloween sale
3 - Geissele Super Semi-Automatic Enhanced (SSA-E) - on sale for $194 through Trading Place Pawn. Price included shipping and no tax.
4 - DPMS LPK minus FCG - http://www.brownells.com/rifle-parts/receiver-parts/parts-kits/308-lower-parts-kit-minus-fire-control-components-sku231000334-27207-111705.aspx

Got it for $50
5 - A5 receiver extension - http://www.brownells.com/rifle-parts/receiver-parts/buffer-tube-parts/buffer-tubes/a5-receiver-extension-sku100010797-55056-111100.aspx

Paid $47.50
6 - STR stock -   http://www.brownells.com/rifle-parts/stock-parts/buttstocks/str-mil-spec-stock-black-sku100009321-45226-102656.aspx

paid $76
7 - Noveske QD end plate    http://www.brownells.com/shooting-accessories/slings-sling-swivels/tactical-sling-mounts/qd-receiver-end-plate-sku100004756-31766-57871.aspx

cost $27
8 - Magpul MIAD 1.1 grip     http://grabagun.com/magpul-mag520-blk-miad-gen-1-1-grip.html

paid $28
9 - BCM Low Profile Gas Block (steel with set screws) 750    cost $45
10 - BCM mid length gas tube $13
11 - Larue Tactical A2 flash hider for 308 - $20
12 - Aero Precision 308 complete BCG(follows DPMS pattern)    http://aeroprecisionusa.com/aspx/store/productdetail.aspx?pid=175

cost $195
13 - Rainier Arms 308 Match 16 inch Barrel DPMS pattern   https://www.rainierarms.com/rainier-arms-matchtm-308-barrel-21

cost $315
FYI if you buy a barrel from Rainier, you don't have to buy the BCG through them to get free headspacing. Call and they'll tell you how to add this to your order
14 - AR 10 buffer spring - $10
That got me to right at $1,750 for the base setup I want for way less than the LMT, Larue, or FN. I could have gone much cheaper in a few area to keep the cost down such as going with Aero Precision receiver set, use the trigger and grip that comes with the DPMS LPK, Rainier Select barrel instead of Match barrel, etc... That would have probably saved several hundred bucks, but I would not have been as happy. My pictures don't do it justice. This is a great looking setup and I'm excited to go break it in soon.
I will likely do a few other things, such as Raptor, BCM, or Mecharmor TacOps1 charging handle (would be interested to hear you opinions on which is better), a good light never hurts, etc.... But I have the foundation I want and I'm quite certain I'll save money vs. the LMT, Larue, or FN routes.

Very nice indeed. <thumbsup>

Question though, how do you get the head spacing done IF you're not buying the bolt from them? Did you send in your Aero bolt to them, to head space it to your Ranier barrel? <dontknow>

Edited November 26, 2014 by Christopher67

Bang4Buck · November 26, 2014

Very nice indeed. <thumbsup>

Question though, how do you get the head spacing done IF you're not buying the bolt from them? Did you send in your Aero bolt to them, to head space it to your Ranier barrel? <dontknow>

Yep. I shipped the bolt to rainier and they shipped it back with the barrel. Local gunsmith I use verified the headspacing as well.