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Thread: BCG binding in upper

  1. #21
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    UPDATE:

    I don't think the upper is the problem. The carrier moves freely when stripped, and when the bolt binds up, the carrier is still able to move.

    Upon closer inspection, I can see a few burs on the lugs of the barrel extension. The lugs on the bolt show corresponding wear patterns. I've contacted CLE to request an exchange. I'll update when again when I hear back.

  2. #22
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    ETA: Just read your update - seems you are on the right track.

    Quote Originally Posted by guitarist1993 View Post
    the BCG would get about 95% of the way forward before locking up while still out of battery.
    If it is closing that far... the carrier is probably not the problem, I would suspect the bolt is binding in the barrel extension.

    Quote Originally Posted by guitarist1993 View Post
    A little wear inside of the upper around the cam pin slot and just underneath the CH slot
    Checking out the wear marks here... further indicates your issue is in the bolt to barrel extension lock up.

    Quote Originally Posted by guitarist1993 View Post
    There's no way in hell we managed to break the barrel extension loose putting the muzzle device on.
    I've seen lots of guys do it... not as rare as you might think.
    Please let me know if I have offended you...
    I would like to move on to my next task.


    I provide legal consultation and training - specializing in the Law of Gravity.

  3. #23
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    Quote Originally Posted by K.L. Davis View Post
    If it is closing that far... the carrier is probably not the problem, I would suspect the bolt is binding in the barrel extension.


    Checking out the wear marks here... further indicates your issue is in the bolt to barrel extension lock up.
    Yep. I imagine the wear I'm seeing on the charging handle and inside the upper is just a result of the MUR's tighter tolerances, combined with me cycling the handle so much during troubleshooting. Having to mortar it to free the bolt is likely exacerbating the wear as well.

    So I guess this is good news, since that means the upper wasn't out of spec or somehow torqued.

  4. #24
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    Quote Originally Posted by guitarist1993 View Post
    Gas tube is straight.



    A friend of mine who has more experience building uppers helped me. We used a clamshell type clamp to hold the upper and an insert that simulated the placement of a gas tube, but I don't think it offered much support. That said, I find it hard to believe an MUR would be that easy to torque this badly. The barrel nut is at 50lbs.

    So am I shit out of luck if that is the problem?
    What clamshell vise block did you use on a MUR? I was under the impression that MURs are not compatible with clamshell vise blocks. If you used a standard clamshell vise block, it is likely that you crushed the receiver a little.

  5. #25
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    Quote Originally Posted by Hookuleez View Post
    What clamshell vise block did you use on a MUR? I was under the impression that MURs are not compatible with clamshell vise blocks. If you used a standard clamshell vise block, it is likely that you crushed the receiver a little.
    After the recent updates, I'm pretty sure it's not the upper. The burs on the barrel extension and wear on the bolt all point to it binding in the extension. When it locks up, the carrier is still able to move slightly when I pull on the CH.

    I spoke with Compass Lake today and they said it's a rare but known issue that they've had before. I'll send it in this week.

  6. #26
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    Quote Originally Posted by K.L. Davis View Post
    ETA: Just read your update - seems you are on the right track.


    If it is closing that far... the carrier is probably not the problem, I would suspect the bolt is binding in the barrel extension.


    Checking out the wear marks here... further indicates your issue is in the bolt to barrel extension lock up.


    I've seen lots of guys do it... not as rare as you might think.
    Then they were either being ridiculous, or the gun was not build correctly, IMO. However, my statement is assuming a Geissele reaction rod vs. clam-shell which transmits all of the pressure to the upper vs. containing it "within" the barrel extension like the Reaction Rod.

    Have you seen otherwise?

  7. #27
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    I've purchased and installed several (around 18-19) AR barrels from CL. Never had an issue EVER.

    With that said, I always get properly headspaced bolts at the same time.

    Do you have another bolt around the house? Would be interesting to see if a different bolt gave you better/worse results.

    Good luck.
    Quote Originally Posted by markm View Post
    But you should have enough mags that you don't need to see a grief councelor if you destroy or damage one.

  8. #28
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    Tried a PSA and a Rainier bolt in addition to the properly headspaced one from CL. Same thing. Compass Lake said it's a rare issue they've run into before since they don't make the extensions in house.

  9. #29
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    My sons Bull Barrel rifle had a binding bolt issue that was caused by stack tollerances in the timing of the bolt to extension. I swapped out a different CARRIER and the concern went away. The root cause of that issue was the cam pin slot was at the minimum spec and the extension was just enough to prevent lock-up. I put a Spike's carrier in it and the bolt would clear the lugs and lock up.

    Do you have a different carrier to try?
    Honesty, Honor, and Integrity Are Everything!

  10. #30
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    I did try my PSA carrier, I don't remember if I tried it with the CL or Rainier bolt though. The barrel's back at CL now, so I'll have to wait till next week to see if that fixes the problem.

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