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Build a Light Weight 308 AR


imschur

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1 hour ago, sketch said:

reaction rod ! simple and never wears out.. in my house. 98's maybe..

 

1 hour ago, washguy said:

Sketch.....remember that big ol long thread about the reaction rod ?   the pros and the cons?    :thumbup:   Wash

 

3 minutes ago, sketch said:

ive slept since.. bro its not in the tools section?

Geissele Reaction Rod.  Done.  Solved.

Pick one - they make them in both versions, which covers you in anything you will ever do in ARs...  Done.

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Oh, just for the record, the MagPul Armorer's Wrench is the baddest motherfucker on the planet. I've used alot of them over the years, but this one smokes them all. By far.  :thumbup:

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  • 2 months later...

So I finished rebuilding my .308 project after welding and pinning the muzzle device last night (poorly I might add, lol). The guns previous setup was carbine gas and the extraction was premature with excessive carrier velocity as well. Extraction reliability was sketchy and it beat the poop out of brass even more than a regular 308AR.

 

I think this setup should cycle a whole lot better than my last carbine 14.5”; the bolt/barrel headspaces perfectly between a GO & NOGO, the midlength gas is longer and the port is also 0.010" smaller. While I was changing the barrel and bolt, I also replaced some of the ergonomic bits, too.
 
Put the whole thing on a scale and it's exactly 8.75# unloaded with optic (7.83 LB without optic). It balances nicely at the magwell, too. I’m sure there’s lighter “lightweight” setups, but this ones full featured and still decently light considering it’s not using anything exotic. Typical barrel/BCG, stock and handguard.

 

If it functions well, it will make a hell of a DMR out to 500-600 with 155gr AMAX, but still small and light enough for dynamic shooting inside 100yds. 

 

Parts:

Black Rain billet set populated with DPMS parts.
Ballistic Advantage Premium Series Barrel (16” middy cut to 14.25")
Ballistic Advantage factory pinned gas block & tube
Ace Entry Stock with Slash Heavy buffer and JP carbine spring. 
Toolcraft BCG with installed RCA Adjustable Gas Key
JL Billet 12.8" Mlok Handguard
Magpul K2 grip (spare battery & torx in grip)
ALG ACT trigger (Larue MBT on order though)
Leupold VX-R Patrol 1.5-4X in Aero Ultralight mount
Magpul MBUS Pro backup irons
Pinned AAC 51T Brake Mount (for a762-SD can)

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Edited by Joeymac
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Don’t know... left it alone at .072”-.073” and I’m going to test it out it Thursday.

Maybe it will run well with a standard toolcraft carrier (without adjustable key) and then either a slash heavy buffer or a standard DPMS carbine buffer. If not I can open it up to .081 and play around with the adjustable gas key from there. 

But it would be cool if I could get it to run with a plain gas block and carrier.

unfortunately, I couldn’t find any weak wolf or ZQI ammo to tune for bolt hold open with. So my weakest loads I’m bringing are DAG and L2A2 milsurp, Freedom remanufacture and MFS steel cases. 

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12 hours ago, 98Z5V said:

Looks damn good!  What did you end up with the the gas port size?

OK, took it to the range and it ran like greased lightning. Lubed it up, ran a lubed patch down the bore, and then started shooting. It cycled everything and locked back on everything. 100 rounds (25% suppressed) and no FTF, FTE, jams or hiccups. No stopping to clean or lube either.  The brass looks clean and not mangled. It shot pretty flat with the just the brake and no silencer, although the blast was sizable. 

 With no silencer it puts brass in a pile about 10 feet away at around 3:00-4:00. Which for an AR15 would be perfect, I'm not sure about an AR10/LR308 though. And with the silencer attached and no other adjustments it actually deposits brass about 4 feet away a the 1:00-2:00 position... which I think that means slightly overgassed, although that wouldn't be surprising considering the silencer. Nevertheless, it still functioned great anyways even with a silencer. I'm surprised it ran so well with no gas regulation at all for either.  

Magical setup: .073" Gas Port, 14.5" Midlength Barrel, Plain Gas Block, Regular Bolt, Slash Heavy Car Buffer (5.6oz). 

At this point, I don't even think it's worth playing around with tuning the gun using the adjustable gas key & lighter buffers. Although I might switch over to an A5/AR10 carbine tube though with a Slash XH Carbine Buffer (8.5oz) and Magpul FCS for a slightly longer LOP.

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