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Modo

Rifle length barrel cut to 16"

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I have a 16 inch 308 barrel that's rifle gassed, I'm having a had time with short stoking. Seems it's running under gassed and needs an adjustable gas block. Any idea what size the barrel gas port should be? Having a hard time cycling ZQI 762 from Walmart.

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It was once wisely pointed out to me that an adjustable gas block can only lower the ammount of gas flow. Makes sense, yeah? So if you need to make adjustments, you'll have to either open up the port, or lighten up the moving parts.

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I have a 16 inch 308 barrel that's rifle gassed, I'm having a had time with short stoking.

 

What manufacturers barrel is this?  Is it a Fulton Armory/Criterion barrel that you're talking about?  If not, who's is it?

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Robocop,

 

Its a DPMS SASS barrel that was 24 inches, bought it from Numrich for $120 and had it cut it to 16 inches and lightened the profile. The Gunsmith opened it up but I don't think it was enough or maybe my gas block is bottle neck.

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Robocop,

Its a DPMS SASS barrel that was 24 inches, bought it from Numrich for $120 and had it cut it to 16 inches and lightened the profile. The Gunsmith opened it up but I don't think it was enough or maybe my gas block is bottle neck.

This is good info to put out up front to help us diagnose the issues your having.

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true, I ordered a Seekins adjustable gas block. Hoping that cures the short stroking, if not im going to have the barrel port opened up. Im thinking of going 0.1095 cause I can always dial it down with the gas block, and can shoot anything no matter how anemic the round is.

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@Modo

 

I have a 17" rifle-length barrel. The gas port was opened up to .099

 

The port inside of your GB can be as large as .125, so opening up to near that size and then adding an adjustable GB  should be perfectly safe.

 

When you had the barrel re-contoured, did you have the area at the gas block redone as well. If memory serves me right, the DPMS SASS has a canted surface at the gas block, and requires a SASS specific gas block. You may have to have that area also redone, perhaps down to a .750, to fit a standard fitting GB.

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  Ya, its tapered or something , there is a thread on it some where here . Unless that part of the barrel was untouched .

  I think the 24 " Barrel will have a smaller gas port than a 16" , there's a lot of Barrel after the port on a 24 ". although, was it opened up enough , that's a good question .

 

  You may also check some basic things also , enough Lubricant on new build ?

 

  DPMS Chambers were notorious for having rough or tight chambers also. Head space been checked ?

 

  As has been asked what stock system & its components , all 308AR ?

 

  Could also be bolt bounce , maybe the port is too large ? 

 

  Does the BCG, hold open on last round ? Try it with one round in the mag & progress to three & see if it holds the Bolt back each test .

 

  Have you tried different manufacturers Magazines ?

Edited by survivalshop

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First off, thanks for starting a thread/moving the posts.

I confirmed that it's the correct rifle length buffer and spring. Buffer is 5.33oz and the spring is 39 coils and 12.75 inches.

I saw that Fulton opens the port to 0.1095 on the 16 inch rifle length barrels. What number drill bit is that? Link to one one Amazon?

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  I have to look up what drill bit size my 16" is . Its in a thread on this forum , some where & I have it written some where in my notes , but it may take me a bit to find it .

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I ran it wet, the bolt holds open on one round.

ran 20 rounds of 147 grain ZQI 762 I got from Walmart. First I put one round in the PMAG and it fired and bolt locked open. I put 3 rounds and fired, round one fired but bolt came back and closed on the spent case. Had to pull the charging handle to eject the spent case and chamber the next round. With the ZQI this was the case with every round.

Next I ran 10 rounds of Winchester 150 grain 308 I picked up oaktrees rifle range. One of the guys shooting there said that the ZQI is underpowered, and try something else. I put three rounds of the Winchester in the PMAG. Fired the first round and it shot fine, spent case flopped out right next to me on the table but it didn't pick up the next round. I had to pull the charging handle to load a live round. This happened with all 10 Winchester rounds.

I'm running a 16 inch barrel with rifle length gas, and a fixed gas tube. When Randal was doing the assembly he drilled the gas hole, maybe it needs to be bigger??

Thoughts?

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When Randal was doing the assembly he drilled the gas hole, maybe it needs to be bigger??

AR15barrels.com Randal(l)?

How's the gas block mounted? Clamp on or set screw? Are there signs of leakage? Have you tried checking the gas block for fit and alignment?

Another thing you can try is using a muzzle device that creates some back pressure so that the system (barrel + muzzle device) has the dwell time of a longer barrel. The Griffin Flash Comp and Bad-Ass Battle Comp do this.

Edited by FaRKle!

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AR15barrels.com Randal(l)?How's the gas block mounted? Clamp on or set screw? Are there signs of leakage? Have you tried checking the gas block for fit and alignment?Another thing you can try is using a muzzle device that creates some back pressure so that the system (barrel + muzzle device) has the dwell time of a longer barrel. The Griffin Flash Comp and Bad-Ass Battle Comp do this.

Yes AR15barrels Randall. Awesome guy, great watching him work. He even mentioned that I would probably need an adjustable gas block.

I checked the block and alignment and it was dead on with no leaks. It's a set screw model, it was $24 ar15/10 model in 0.750 so it fit. Maybe that's the culprit.

I have a ferfrans CQB brake and attachment,

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ran 20 rounds of 147 grain ZQI 762 I got from Walmart. First I put one round in the PMAG and it fired and bolt locked open...

...One of the guys shooting there said that the ZQI is underpowered, and try something else.

 

Those two statements don't make any sense, and you proved it.  "One of the guys shooting there" is wrong.  If the ammo was underpowered, if wouldn't have locked the bolt back on one round.  It's got enough power to cycle the rifle, or that test would have failed - and it didn't. 

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  How does the fired brass look ?  Any Scratches on the side of the brass , Extractor marks ? Inspect the chamber for roughness . Polish if necessary , one would think your Barrel guy would have checked all that , but you never know unless he said so .

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my 308ar which has fed 40 year old south African and middle eastern surplus ammo fine can't manage to put 3 of those zqis downrange without some sort of horrible mishap.

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If I remember correctly, Farkle bought some of that stuff. It ran horribly... But my 17" still ate it up. I have yet to have any serious ammo issues, despite having a rifle length gas system on a 17" barrel.... 17" may be the magic length.

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@Modo, I see in the Calguns Salt Works 308 build and review thread : http://www.calguns.net/calgunforum/showthread.php?t=1036853  

that you have the new Salt Works 308 receiver set - how do you like it? I'm actually considering ordering the set since you can't beat the

price not to mention that they look bad a$$ - you should post some pics for the guys here. I live in santa clarita but, I don't go to oaktree 

much, I prefer to go to "a place to shoot". My 308's are still "under construction" but, getting close - should be out plinking within the next

month or so. Question, when your bolt locks open does the bolt carrier travel back far enough for the catch to engage with the bolt face or

is it possibly catching on the forward edge of the carrier? 

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If I remember correctly, Farkle bought some of that stuff. It ran horribly... But my 17" still ate it up. I have yet to have any serious ammo issues, despite having a rifle length gas system on a 17" barrel.... 17" may be the magic length.

Nope. I bought CBC/Magtech M80 ball. Awful stuff that's loaded HOT. I like their 5.56 loads though.

My LMT MWS 16" rifle-gassed barrel runs well, though the CBC stuff still showed high pressure signs.

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