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They say patience is a virtue . . .


Slugger

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Unfortunately I've got none of it! Thanks to the info ya'll have left around here I'm well on my way. I've got a pile of parts now and a few more to get ordered before I can cobble this boomstick together. Here's where I'm at:

Parts in house:
BCG Toolcraft DLC coated
Barrel Criterion SS nitrided hybrid 16" rifle gas
Muzzle CMB-Q6
GB SLR Sentry 7
Recoil assy Armalite kit # AR10REKIT01 Strange that this kit came with an ambi looped end plate? I hope the rest of the kit is right, I ordered this directly from Armalite.

Barrel finally showed up tonight, so out the the shop I went. Headspace checked out good so I'm killing time till the builder kit I want is back in stock.

Waiting on:
LaRue MTB-2S trigger backordered

To order:
BCM Mod3 CH
AP Freedom M5E1 Mlok 15" builder set
AP LPK
Want another Bobro mount and Strike Eagle 1-8 for optics
Pmags and/or Lancers

Still to decide on: For the stock and grip I'll just use some other parts I have on hand. Probably just a CTR and K2, but those SOPMOD stocks look comfy.

 

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I'm curious how this rifle will shoot. Your setup is very similar to one I've got slowly coming together in my parts drawer (looking at a Criterion/ADM hybrid contour 16" rifle gas, rather than the nitrided SS you're running).

I'm mainly wondering whether or not an adjustable gas block (I, too, have an SLR Sentry 7 waiting for a rifle) will be necessary on a 16" rifle gas setup. My 5.56 "true dissipator" (16" rifle gas) rifle is under-gassed, but I'd imagine a .308 would be a different animal altogether.

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16" rifle gas .308 barrel will have to have a gas port diameter of 0.100"~0.105", or it's not gonna run.  Check your gas port diameter on that barrel. 

Criterion understands this, as they were one of the first ones to make this config, for Fulton Armory.  Check it anyway.

Edited by 98Z5V
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I hear you washguy, I hope it doesn't end up too heavy. After building a few dozen FALs I would bet it would be lighter than that system, but it can add up fast.

It will be a while before I get the upper/lower etc together and test her out COBrien, but I'll keep ya'll up to date on how she does. Looks like the ADM hybrid is pretty close in weight unless the spec I saw was goofed up. I'm not sure what to expect with the gas system but I have long term plans for a couple cans in my future. I am hedging my bets on the adj gas block. Probably not required? We'll see.

98, I followed your guidance on the recoil system. I'll have to recheck the port size. I tossed my calipers on the port but don't recall what it was. I want to say it was only 80 thou ish but I'll double check. I know that the FAL with a full size barrel liked 98 thou but I remember some that chopped to 16" having to open it up a bit. IIRC gunplumber gave a top end size of about .125" before they started shaving. Have others had to open up these Criterion 16" barrel ports much? The FAL is a different beast but it wouldn't surprise me if they were close in required gas. Of course FAL isn't a DI system though.

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1 hour ago, Slugger said:

OK took another look. I don't have any ball gages but with my calipers I get a repeatable .079" on the gas port. Seems a little on the small side doesn't it?

Yeppers     that's on the small side for sure  my 16" middies are all .082 to .086ish     Wash

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2 hours ago, washguy said:

Yeppers     that's on the small side for sure  my 16" middies are all .082 to .086ish     Wash

^^^ ...And those are midlength gas barrels...

Hit this info, check out survivalshop's info - his Fulton Criterion 16" rifle gas barrel is in here:

 

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14 hours ago, Slugger said:

Yeah I guess it's time to get on the horn with Criterion

Nope, save the time.  Just drill it up.  :thumbup: Toss a 1/4" wooden dowel down the barrel to protect the other side, if you get heavy with the drill hand. 

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3 hours ago, 98Z5V said:

Nope, save the time.  Just drill it up.  :thumbup: Toss a 1/4" wooden dowel down the barrel to protect the other side, if you get heavy with the drill hand. 

Easy Peasy  .....if you can chew gum and walk at the same time you are GTG    :banana:   Wash

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My 17” rifle length is .099”

I cut some new barrels and had to open them to .105 and .110

honestly, you can only really open up to about .115 effectively. The gas block is only .125 in diameter. Drilling a barrel to .115 or even .120 only leaves you a .005 to .0025 shelf to get centered. If you drill the barrel port to .125, and you don’t get exactly centered  you’re likely to have at least .0025 offset on each side. 

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Ha, any of you one eyed, late night drillers ever try a reamer or dreamer? I've opened up quite a few FAL barrel ports but they are deep inside the gas block so it was better controlled to ream it out. I had one bit snap and had to take it to an EDM guy to have it burned out. Ever since that episode drilling ports gives me the heebegeebies.

Safe to assume drilling up the port voids any Criterion warranty?

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  • 5 months later...

Yup you guys were absolutely right. I figured as much, brass fte then adjusted gas block and got it to eject but would never hold the bolt back. Opened her up tonight with a .097 for another try. Got the barrel broke in and scope sighted in. Ready for final adjustments now. I frickin knew that .080 was too damn small. Are they making these barrels work with super light springs and light bcg or something?

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1 hour ago, Slugger said:

I frickin knew that .080 was too damn small. Are they making these barrels work with super light springs and light bcg or something?

 

Only if it's a race gun.  It's a mistake on their part on the gas port sizing.  16" rifle-gas in a .308 is a tough one to pull off.  When they made them for Fulton Armory, the spec given to them was 0.105" - and they built what was ordered.  Fulton barrels functioned fine. 

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