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Thread: Gas block seepage?

  1. #1
    Join Date
    Nov 2010
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    Default Gas block seepage?

    I test fired an AR I built up and accuracy seemed horrible. Turned out there were some serious issues with the scope which I may or may not have fixed at this point. Accuracy got to a tolerable level after some adjustments.

    I noticed something I have never seen before though. There seems to be some blowby from under the gas block. There was a heavy streaking of oil/carbon residue coming from under the front and rear of the gas block to about 1/2" out.

    How serious a problem is this?

    I didn't expect anything like this as, when I duracoated the rifle I had removed the gas block. When I put it back together the gas block was so tight I had to sand down the duracoat, oil the barrel and then tap the gas block on with a drift.

    Any advice? do I need to do anything about this?
    I own firearms not to fight against my government, but to ensure I will not have to.

  2. #2

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    I have also seen this on my service rifle. It does not seem to be affecting accuracy. I'd like to know if there is a fix myself.

  3. #3
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    I have a light colored camo scheme on this one and I kind of wondered if this is normal and I just never noticed it before on darker rifles. It might be that after a few hundred more rounds the carbon will seal it up. Had the gas block not been so tight I probably wouldn't think much of it.
    I own firearms not to fight against my government, but to ensure I will not have to.

  4. #4
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    I have one with a stainlless heavy barrel and never noticed any discoloration or carbon around the gas block.

  5. #5
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    I had thought that maybe the gas hole was partially obscured thus causing the pressure to go where it shouldn't. The rifle functions flawlessly though so i know it cannot be much obstruction. I may try to bump it forward just a hair. If it is not centered it is likely too far back due to how I set it up when reinstalling.
    I own firearms not to fight against my government, but to ensure I will not have to.

  6. #6
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    I had an Olympic upper on my match rifle that leaked that way from the 1st shot until I junked the barrel at 5000+ rounds. The gas block was a cut down GI that was discarded with the barrel.
    Ugly green build up that didn't hamper function any. I would leave it unless the cosmetics bother you.

  7. #7
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    This is fairly common, and usually "self-heals" after a number of rounds have been fired as residue builds up in the space between the gas block and the barrel. I wouldn't mess with it if the rifle is working OK. Has no effect at all on accuracy.

  8. #8
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    Quote Originally Posted by tpelle View Post
    This is fairly common, and usually "self-heals" after a number of rounds have been fired as residue builds up in the space between the gas block and the barrel..
    Ok, That's what I figured and just wanted outside confirmation. Was also thinking that the tighter the fit the more pronounced the blowby will appear as it would retain more pressure on the way out. I probably put about 80rds through it was all, now that I think about it.
    I own firearms not to fight against my government, but to ensure I will not have to.

  9. #9
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    blow by is pronounced on front sights that are adjustable. They have to fit loose to adjust. Compass lake states, if there is a cycling problem from too much blow by, squirt some lock tight under the sight base where its leaking. Worked for me.

    hth; regards, dennis

  10. #10

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    Thanks for the tip. I'll be trying it myself.

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