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AR Experts; How big a problem is this?

Discussion in 'Rifle Country' started by berettaprofessor, Sep 1, 2019.

  1. berettaprofessor

    berettaprofessor Member

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    Just noticed my stock Stag 6H 223 upper (Hogue handguard, stainless bull barrel, low profile gas block) is throwing some carbon around the gas tube from the gas block (see pics). The rifle has about 300 rounds through it and I haven't noticed this before but won't say it's impossible that I've missed this a few cleanings since it's almost under the handguard. The tube is pinned in the gas block and neither appear to have moved since manufacture. Love this rifle, and it shoots one-hole groups despite this.

    How big of an issue is this? I've never run into it but assume the gas tube will erode there and the problem may get worse? Is there an easy fix without replacing the gas block and tube?

    IMG_1977.JPG

    IMG_1976.JPG
     
    Rollis R. Karvellis likes this.
  2. edwardware

    edwardware Member

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    If your AR isn't leaking at the block and tube, then you're not using it (or you aren't looking). All AR's leak, and will tend to leak less over time as carbon buildup seals the leaks.

    If you're happy with the accuracy, I would strongly discourage touching it.
     
  3. JeffG

    JeffG Member

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    ^^^ This. Nothing to worry about.
     
  4. Demi-human

    Demi-human Member

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    If everything works properly, I see no problem.

    As far as erosion, think about where the wear and erosion begins in the barrel. That's a long way from the port. By the time tha port or gas block wears, the barrel has.

    Some adjustable blocks have aluminum restrictions that erode fairly quickly. Adjust the piece till it wears out, replace. Replace the piece till the block wears out, replace the gas block.

    I hope you enjoy your upper.
    Happy shooting!:)
     
  5. Shanghai McCoy

    Shanghai McCoy Member

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    So an AR is like a Harley? o_O
    It only leaks when it's running..? ;)
     
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  6. mokin

    mokin Member

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    Every AR-15 (and M-16 for that matter) I've used has had a similar "leak". "If it ain't broke...".
     
  7. BigBore45

    BigBore45 Member

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    Good to go. She will seal up with carbon deposits. If its functional leave it be. Like they say if it isn't broke dont fix it.
     
  8. taliv

    taliv Moderator Staff Member

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    I just checked 5 ARs I have used in classes and matches that have between 500 and 20,000 rounds on them. None are leaking like that. So I disagree that all leak like that.

    However, i don’t think it’s a problem for you as long as it’s functioning fine now. Check the ejection pattern.
     
  9. Pat Riot
    • Contributing Member

    Pat Riot Contributing Member

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    Mine have all leaked like that except 1. It was a piston upper.
     
  10. berettaprofessor

    berettaprofessor Member

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    Thanks all; I'm reading the consensus to leave it alone as good news. I haven't noticed this on my other AR's, but I've only got one other with a stainless steel barrel; maybe I'm just not noticing it on parkerized barrels and, frankly, most of my gas blocks are under the handguards so I can't easily see them.

    Taliv, this gun ejects straight at 2:00, about 6 feet out when I'm shooting prone, small pattern, 10 cartridges yesterday during a chrono test all within about a one foot diameter circle.
     
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  11. Nature Boy
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    Nature Boy Contributing Member

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    I think you answered the question :thumbup:
     
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  12. FL-NC

    FL-NC Member

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    No problem.
     
  13. greyling22

    greyling22 Member

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    I never noticed any leaking on my pinned gas blocks, but I got a couple wojtekadjustable gas blocks that both leak. it's not a big deal and it does seal up. faster if you use a can. I prefer to think of it as a feature, not a bug. Superlative arms charges a lot of money for a "bleed off" adjustable gas block and I got one for free......
     
  14. berettaprofessor

    berettaprofessor Member

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    I checked several of the black AR's. A couple have some carbon deposit; just under the handguards where I can't see them. Not as much as this one though.
     
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  15. Demi-human

    Demi-human Member

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    And they all run, too?;)

    Eta:
    Run them, love them, relax!:)

    My VR-Eighty exhausts radially inside the hand guard. Fortunately for me, supersonic gases vent directly under where I hold it. :confused:
    Gloves are necessary.

    Wipe it off with a rag so it doesn't get in your rifle case.

    I guess there's around a thousand pounds of pressure at the gas tube. But I can't remember how I came about that.

    Both my piston ARs vent at the block and have residue deposited there, similar to yours. So I suppose it was not a big deal to me. I didn't mean to sound dismissive.:)
     
    Last edited: Sep 2, 2019
  16. berettaprofessor

    berettaprofessor Member

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    You weren’t. I fully recognize that although I’m learning all the time, in many things gun-related, I’m a novice. And I really hadn’t seen any discussion about ARs leaking before.
     
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  17. cougar1717

    cougar1717 Member

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    Just think about the fluid dynamics of what is going on here. The pressurized gas in the barrel, between the time the bullet passes the gas port and when it leaves the muzzle, is taking the path of least resistance. It goes up through the gas port in the barrel. Some gas may find it's way out between the gas block and barrel (even if alignment is perfect). The gas goes through the gas block and into the gas tube. Some gas finds it's way out between the gas block and the gas tube. Enough gas (hopefully) travels down the tube and hits the carrier key, providing the force to cycle the rifle.

    Neither the mechanical fastening of a gas block to a barrel or the gas tube to the gas block provides a complete seal. If it could, plumbers would use roll pins and set screws (haha).

    There is very little control over the leakage between the gas tube and the gas block. Tubes that have to be jammed into place to align the roll pin **probably** leak less. Looser fitting ones **probably** leak more.

    The gas leakage between the barrel and the gas block may be able to be reduced IF the port on the gas block isn't fully aligned with the port on the barrel. The gas block port is bigger than the port on the barrel, so you typically have some slop to work with. In this case, the rifle cycles correctly, so no corrective action is required. However, if the rifle was short stroking, the first place to look is the alignment and attachment of the gas block. I have had a gas block that was set screwed without dimples drilled in the barrel come loose no matter how tight the screws were tightened or how much loctite went on those screws. It got replaced with a clamp on style block. No issues after that.

    Additionally, aluminum gas blocks eventually leak (and wear out) quicker since the gas port gets enlarged faster simply due to the materials involved. It is still a lifespan in the thousands of rounds.

    Final thought - it's easier to see the leakage on a stainless barrel due to the color difference. Matte black carbon leakage is harder to see on a matte black barrel.
     
  18. Corpral_Agarn

    Corpral_Agarn Member

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    Meh.

    Like others have posted, if you don't see any of that, it's probably a new rifle.
     
    Demi-human likes this.
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