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Thread: AR not unlocking

  1. #11
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    Quote Originally Posted by QuadBomb View Post
    All,

    The BCG was slightly out of battery and it wouldn't move when I pulled on the charging handle. I dropped the magazine and tried to clear the chamber. I had to pull extra hard on the CH for the BCG to come loose, and the empty brass then ejected out the port.
    I had this same problem with a AR15 Performance Recon Upper 16". I sent the upper back to ARPerformance and a new BCG was installed due to a possible headspacing issue.
    That seemed to resolve the problem, but I thought it was still a bit "sticky". I ended up selling the barrel and installing a Wilson barrel and have not had any problems with the upper in its current configuration using the same BCG.

  2. #12
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    Quote Originally Posted by QuadBomb View Post
    I think I've found the culprit.

    The gas block is loose. I was able to cant it to either side as far as it would go before the gas tube touched the forearm, just by using my wrist. I took pictures:

    Untouched


    And now, after I twisted it with my hands

    Bottom view


    Top


    Side


    Also, it appears that the gas block has slid forward of its intended position. That rim on the barrel should be flush against the back wall of the gas block, the way I remember it.

    Looks like this one is going back to the shop from whence it came. I hope nothing else happens - this is the second time I've had problems with this upper receiver.
    Glad you found an obvious flaw. But this still doesn't explain why manual extraction is difficult.

    Send it back and get it fixed. But make sure they give the weapon an entire once over and address all the problems. Don't let them just tighten the gas block and call it good.

  3. #13
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    I think I've found the culprit.

    The gas block is loose. I was able to cant it to either side as far as it would go before the gas tube touched the forearm, just by using my wrist. I took pictures:

    Untouched


    And now, after I twisted it with my hands

    Bottom view


    Top


    Side


    Also, it appears that the gas block has slid forward of its intended position. That rim on the barrel should be flush against the back wall of the gas block, the way I remember it.

    Looks like this one is going back to the shop from whence it came. I hope nothing else happens - this is the second time I've had problems with this upper receiver.

  4. #14
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    Quote Originally Posted by Dr Dues View Post
    Need to check:

    1) Gas Key
    2) Gas block
    3) Gas Tube

    anyone of these could cause you issue. If your gas block uses a set screw or clamp to hold it in place, the block could have shifted. the roll pin holding the gas tube in place could have fallen out. Finally broken gas key screws cause the issue as well.
    How does that make it harder to extract the fired casing?

  5. #15
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    Quote Originally Posted by Guilty View Post
    BCG <snip>headspacing
    why not just the bolt?

    Sounds like the space between the end of the barrel and the inside of the extension was too small.

  6. #16
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    Quote Originally Posted by jmart View Post
    Glad you found an obvious flaw. But this still doesn't explain why manual extraction is difficult.

    Send it back and get it fixed. But make sure they give the weapon an entire once over and address all the problems. Don't let them just tighten the gas block and call it good.
    Wow, how did your quote get ahead of my post in the thread? Never seen that before.

    I hand-cycled it a couple times last night and it had no problems. If I had to guess, manual extraction was difficult because the gas block was out of alignment with the gas port, so the gas system was not working at all when I fired. The BCG was probably driven back and partly unlocked just by the force of recoil.

    At any rate, yes I do intend to have them check the whole thing over. ARP is good about fixing problem weapons but I'd rather not have any more problems at all.

  7. #17
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    Quote Originally Posted by QuadBomb View Post
    Wow, how did your quote get ahead of my post in the thread? Never seen that before.
    Yeah, that was weird. At the time I posted, your post with pics was displayed, that's how I quoted it. Then I posted and it got sandwiched inbetween. Not only that, but my post was logged an hour earlier than your last post. I went, WTFO?

    Glad you're getting things sorted out. Good luck.
    Last edited by jmart; 08-05-11 at 09:31.

  8. #18
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    Quote Originally Posted by Hmac View Post
    How does that make it harder to extract the fired casing?
    OK, This is a shot in the dark but here are two ideas, either:

    1) the barrel extension, chamber or BCG are extremely dirty thus causing the bolt to bind,

    or, more likely,

    2) when the cartridge is fired, the brass expands in the chamber creating a seal. In normal operation the gas pressure cycles the weapon and overcomes that seal and the extractor pulls the spent casing and extracts it from the weapon. If the gas pressure is insufficient to cycle the weapon, I can understand it being more difficult to manually extract the expanded casing. And all those three (gas key, gas block, gas tube) directly relate to the process of cycling the weapon.
    Last edited by amd5007; 08-05-11 at 10:11.

  9. #19
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    Ok, I wasn't expecting that

    I just got off the phone with ARP. I described my problem and the guy on the phone told me that sometimes the gas block set screws come loose when the barrel heats up. I told him I've had this upper for nearly a year and I've shot it in a 3-gun match before, never had this problem. "Is that it?" I asked. "Just tighten the screws?" Guy told me yes, just keep on 'em to make sure they are tight.

    I don't know what to make of this, but it doesn't seem good to me. I've never heard of that happening on a well-made AR before. I don't even know what screws he's talking about, I thought the gas block was pinned into place.
    Last edited by QuadBomb; 08-05-11 at 14:55.

  10. #20
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    In the photos you posted above, the second one shows the setup from the bottom. Aren't those set screws I see?
    Steve

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