Gas block aligning issues

Discussion in 'Gunsmithing' started by sobi1998, May 3, 2017.

  1. sobi1998

    sobi1998 Active Member

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    I've had gas block issues lately on my AR-15. The way I decided to attach it was to leave the BCG in the receiver and slide the gas block on until the gas tube meets the gas key on the BCG. Ive noticed that if the set-screw hole and the dimple were perfectly lined up, the tube would push on the BCG and take it out of battery.
    So basically if the the tube is against the BCG without pushing it, the block has a gap between it and the shoulder but not lined up with the dimple
    If the hole and the dimple are lined up there is no gap between it and the shoulder but it forces the BCG back

    I noticed the dimple and the gas port on the barrel are lined up vertically. So if it only covers half the dimple, it only covers half the gas port?
    What do y'all think?
    [​IMG]
    [​IMG]


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  2. Vec

    Vec Well-Known

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    that's too far away from the shoulder IMHO.

    stick the set screw in in the dimple
     
  3. sobi1998

    sobi1998 Active Member

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    I get what you're saying but I noticed that if I do put it against the shoulder, the BCG is pushed backwards and won't be fully closed. Almost as if the gas tube might be a hair too long
    I would show a video of what I mean if I could figure out how to
     
  4. Vec

    Vec Well-Known

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    put it in the set screw, and let the bolt go home from the BHO.. it will go into battery, unless you either have the wrong length gas tube, an out of spec gas tube, out of spec gas block, or the gas tube roll pin is not thru the hole in the gas tube ( although that should be blatantly obvious.)
     
  5. sobi1998

    sobi1998 Active Member

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    I did some simple measurements and the block should be against the shoulder to get a perfect alignment. It's just bothering me that the tube pushes the BCG backwards when I push it to the shoulder. I'll have to try both ways and see which actually works. The biggest issues I've had was it wasn't cycling stuff like hornady vmax .223 but it'd cycle m855 just fine


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  6. sobi1998

    sobi1998 Active Member

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    Mar 18, 2016
    Also, I noticed when I have it against the shoulder. The BCG seems to get stuck on the gas tube. As in maybe it's just a tad too far into the gas key and it's getting stuck
    I'm having to Mortar cock it to get it open!


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    Last edited: May 3, 2017
  7. Vec

    Vec Well-Known

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    did you build or purchase the upper already assembled?

    what is the general round count ?

    if it runs on 5.56 but not .223 do you know what size gas port?
     
  8. sobi1998

    sobi1998 Active Member

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    I bought it assembled. It would never Ford more than 2 rounds in a row without failing
    I don't know what size. The barrel is stamped 5.56 not 5.56/.223


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  9. Mikewood

    Mikewood Well-Known

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    Probably a Simple fix.
    Replace the gas tube.
    If you are sure this one is installed correctly and the gas block is in position then the tube is likely too long.



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