New ar10 build

Thebear_78

Private
Minuteman
Jun 5, 2018
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6
I’m putting together the parts for an AR10 build.

Gibbz side charging upper/lower set
Proof 18” carbon fiber barrel
Magpul moe+ grip and CTR stock w/ 1/2” riser
Giesselle SD3G trigger
Superlative arms adjustable gas block
Brownells DPMS style bolt carrier group w/jp bolt
Aero m5 handguard

I’m going to mount a Burris XTRII 1.5-8 on it.
I’m actually building the rifle around the optic, I had it on a 450 bushmaster but didn’t seem worthy of the scope.

Anything I’m missing? Parts should start arriving this week.
 

elmuzzlebreak

Sergeant of the Hide
Belligerents
Minuteman
Oct 15, 2018
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Buffer system is all I am not seeing here. Just make sure you get a full mass system. Proof barrels can be finicky with silent capture systems.

Muzzle device.
 

Coffee_and_Pipes

Private
Minuteman
May 6, 2018
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Denton, TX
It’s always in the back of my mind to try building a large frame AR. Is there much play between the upper and lower with the Gibbz set? Also, how tight was the fit between the barrel extension and receiver? Thanks for sharing your build with us.
 

Thebear_78

Private
Minuteman
Jun 5, 2018
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Well it’s accurate but it not cycling. It’s short stroking. It’s only ejecting 20% and not picking another round up.

I picked up another non adjustable gas block to try out, I also grabbed a couple different buffer weights and a lighter buffer spring to try.

I’m wishing I had gone with the jp lightweight bolt carrier.

I’m guessing it’s undergassed but I really don’t want to go drilling bigger ports in the proof barrel if I don’t have to.

Any ideas?
 

Ravenous

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Minuteman
Mar 10, 2019
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It’s always in the back of my mind to try building a large frame AR. Is there much play between the upper and lower with the Gibbz set? Also, how tight was the fit between the barrel extension and receiver? Thanks for sharing your build with us.
I can't comment on the Gibbz lower and upper receiver mate together but I have the Gibbz upper on a Next Level Arms lower for my current 6.5CM build and the machining and fit is outstanding. I was worried because Gibbz wasn't a very well known company but couldn't be happier with it so far. Haven't shot it as I'm still waiting on some parts but the barrel extension to receiver fit is nice and tight as well.
 
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bfoosh006

Sergeant
Belligerents
Jun 13, 2007
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New gas block and lighter buffer has it running correctly.
Nice.

Its a rarity to have a Large Frame AR be under gassed.

After it fully breaks in, you might try the SA Adj. GB / heavier buffer again.

Start with the buffer first since that is easiest.

( That is how rare a Large frame AR being under-gassed is to me ! Lol )
 

Thebear_78

Private
Minuteman
Jun 5, 2018
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6
The only down side was if I used my suppressor it was way over gassed and sprayed gas into your face, if adjusted down to limit that it would short stroke without the suppressor.

I decided to just run this one sans suppressor.

Accuracy isn’t quite what I expected from a proof barrel. The best accuracy I have gotten was with 175gr federal gold metal match, averaging just under 1” for 5 shots st 100 yards. Several other loads run in the 1.25-1.75” for 5 shots.

The one happy note is that everything from 147gr ball, 150 fusions, 155 Hornady HPBT, 168 SMK and Hornady HPBT, and 175gr SMK all print into a 2.5” group right to the same basic POI.

Any ideas to wring out a bit more accuracy?
 

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bfoosh006

Sergeant
Belligerents
Jun 13, 2007
528
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49
PNW
Accuracy wise.. try shooting off a bag ( I shoot much better off a bag than a bipod.. )

Let the barrel break in more.. try 168gr FGMM, Hornady 155gr Amer. Gunner.

Did you try lapping the upper receiver face ?

Make triple sure all of the scope mount screws are torqued correctly / fully.

Make sure the gas tube can freely go through the upper.. as in, rattle is good through the upper.

Upper to lower snug enough ?

Make sure the hand guard is slightly off of the upper.. a little gap is better then a tight fit .

And ample room around the GB and inside of the free float handguard... if the GB is bonking the handguard.. that is bad.
 
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