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Thread: Gas tube contact on barrel nut

  1. #1
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    Gas tube contact on barrel nut

    General Details:

    FCD URF sans FA
    CMT DRT 13Ē
    Criterion Core 13.9Ē
    BCM .625 gas block
    Midlength gas tubes - Aero and Damage Industries

    Itís been probably a couple years since I assembled an upper. But Iíve done more than a few, and I donít recall noticing this issue before. Maybe I just didnít notice.

    Issue:
    The Aero gas tube clearly makes contact with the CMT barrel nut. It does not ďfloatĒ over it. I grabbed the Damage gas tube that I have as an extra, and it actually was now obviously making contact than the Aero was, with some pressure.

    A little googling and a Criterion video point toward bending the gas tube as a valid resolution for this.

    Anyone else bend their gas tubes? Any tricks to it?

    Iím looking to get the most repeatable performance I can out of this upper, so I donít mind doing itís. Just new to me.
    ďGod doesnít need your good works, but your neighbor does.Ē - Luther

    Quote Originally Posted by 1168
    7.5Ē is the Ed Hardy of barrel lengths.

  2. #2
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    Iraqgunz used to use a large flat tip screwdriver.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  3. #3
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    First, are you sure that your barrel nut is aligned perfectly? If not, get one of these. > https://www.specializedarmament.com/...cision-ground/

    Brownells has them too. They aren't as nice, but they work the same. > https://www.brownells.com/tools-clea...ignment-gauge/

    Otherwise, m-guns has a gas tube bender. I'd go that route over the screwdriver method. > http://www.m-guns.com/tools.php
    Last edited by 556Cliff; 07-31-23 at 23:45.

  4. #4
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    Quote Originally Posted by markm View Post
    Iraqgunz used to use a large flat tip screwdriver.
    I am not visualizing thatÖ

    Quote Originally Posted by 556Cliff View Post
    First, are you sure that your barrel nut is aligned perfectly?
    Ö

    Otherwise, m-guns has a gas tube bender. I'd go that route over the screwdriver method. > http://www.m-guns.com/tools.php
    The barrel nut isnít timed, unlike a GI or some others. So impossible to be the issue.

    I actually was looking at that Michigun bender last night! But it looks like it is for adjusting more within the receiver, if Iím understanding correctly. It appears that the issue with mine is further out.

  5. #5
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    The flat blade would be for adjusting within the upper as well.

    Personally, I don't think it'll be a problem as long as your carrier mates up well with the tube. I mean, if you give it a vend to get it off the nut, it will make it dip downward inside the upper, and then you'd have to bend THAT section back up, right?

    I have no problem giving the tube a slight bend, by hand, if needed for good fit though.

  6. #6
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    Quote Originally Posted by JediGuy View Post
    The barrel nut isn’t timed, unlike a GI or some others. So impossible to be the issue.

    I actually was looking at that Michigun bender last night! But it looks like it is for adjusting more within the receiver, if I’m understanding correctly. It appears that the issue with mine is further out.
    Ah, I get what the issue is now.

    Have you tested to see if the gas tube binds up in the gas key?

  7. #7
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    Quote Originally Posted by ViniVidivici View Post
    The flat blade would be for adjusting within the upper as well.
    This is what I meant. I assumed that the upper was complete, or he couldn't know for sure the final position of the tube.

    Isn't alignment checked with an empty carrier and the upper half inverted? It's been a while for me.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  8. #8
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    I was about to install the gas tube, and thatís when I noticed that with the gas block aligned and gas tube straight into the upper receiver, the bottom of the tube was impacting the barrel nut.

  9. #9
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    Quote Originally Posted by markm View Post
    Isn't alignment checked with an empty carrier and the upper half inverted? It's been a while for me.
    That's the final check, to make sure the carrier freely slides all the way forward with little to no resistance and slides out under it's own weight when the upper assembly is tipped rearward.

  10. #10
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    Quote Originally Posted by JediGuy View Post
    I was about to install the gas tube, and that’s when I noticed that with the gas block aligned and gas tube straight into the upper receiver, the bottom of the tube was impacting the barrel nut.
    So is the barrel nut actually partially blocking the hole for the gas tube into the receiver?

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