Movement in upper and lower
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Thread: Movement in upper and lower

  1. #1
    Newbie scott_r's Avatar
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    Movement in upper and lower

    Hi Guys,

    Ive noticed that as the round count go up things loosen up on my XCR. My gas tube rattles but is no big deal but Ive just found that the upper and lower reciever have alot more up and down play then I used to have. I put a piece of tape between the upper and lower and seems to be ok. Is this normal? When the rifle is charged and ready to shoot its all tight. Once the rifle is fired and bolt is closed its quite loose with lots of up and down movement. This is my first black rifle and am wondering if this is normal?

    Cheers!!

  2. #2
    Marksman the tick's Avatar
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    Re: Movement in upper and lower

    The XCR is "loose" compared to some ARs. If it gets looser you might need to be concerned but this seems to be a common theme with the XCR.

  3. #3
    Super Moderator Underground's Avatar
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    Re: Movement in upper and lower

    The gas tube is "supposed" to move, it's not fixed. If you just can't stand it, some folks have very slightly squashed one end a little so that it doesn't do that.

    When the bolt is open it's resting against the bolt catch which is part of the lower, so it will hold some tension there. Out 3, only one of mine is a little loose, but not that much. I know some folks have had a good bit more play.



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  5. #4
    XCR Guru variablebinary's Avatar
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    Re: Movement in upper and lower

    To remove gas tube rattle, tap it with a rubber mallet a couple if times. It will deform slightly and get a more snug fit

    Between the upper and lower, use a tiny strip of skate tape on the lower where it meets the upper. That till tighten up the fit

    The Bolt Catch will rattle less when a mag is inserted.

    I hate rattles, so I eliminated them all on my own XCR
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  6. #5
    XCR Guru meckr's Avatar
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    Re: Movement in upper and lower

    One of the things that make the XCR so reliable is that it doesn't have tight tolerances. Much like the AK47. Unlike the AR.
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  7. #6
    Newbie JSinAZ's Avatar
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    Re: Movement in upper and lower

    I too noticed the play between upper and lower increasing with the round count ;ast year. I was concerned enough to send the rifle to RobArms, where it was ministered-to by Terra. Her verdict: nothing wrong, shim with tape as needed. I find the tape annoying and a potential point of failure, but I have not worked on a more robust solution. Or maybe I need to be less sensitive to a little wiggle.

  8. #7
    XCR Guru Sean K.'s Avatar
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    Re: Movement in upper and lower

    Quote Originally Posted by JSinAZ View Post
    I too noticed the play between upper and lower increasing with the round count ;ast year. I was concerned enough to send the rifle to RobArms, where it was ministered-to by Terra. Her verdict: nothing wrong, shim with tape as needed. I find the tape annoying and a potential point of failure, but I have not worked on a more robust solution. Or maybe I need to be less sensitive to a little wiggle.
    Might try an appropriately sized o-ring over the front nub on the upper receiver like they do on ARs to tighten it up. The green high pressure/temp ones seem to hold up better than standard black ones.

    HTH,
    Sean
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  9. #8
    Newbie JSinAZ's Avatar
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    Re: Movement in upper and lower

    That is a really interesting idea. I hadn't thought of addressing this at the front of the receiver.

  10. #9
    XCR Guru TerraShrewsbury's Avatar
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    Re: Movement in upper and lower

    Quote Originally Posted by JSinAZ View Post
    I too noticed the play between upper and lower increasing with the round count ;ast year. I was concerned enough to send the rifle to RobArms, where it was ministered-to by Terra. Her verdict: nothing wrong, shim with tape as needed. I find the tape annoying and a potential point of failure, but I have not worked on a more robust solution. Or maybe I need to be less sensitive to a little wiggle.
    At the time, that's how things were. They have changed a lot of tolerances and the guys they have been shipping are very tight, solid fits. It time, but the new fits were shipping right before I left. I'm sorry I couldn't do more at the time, I just didn't have anything that would have fit differently.

    When I stopped by RA the other day, the guns I picked up were amazing. You couldn't even see light through the gap. Correction, there wasn't a gap.

    My XCR has a little gap. It has never really bothered me. There's no wiggle, at least. MY FNP 45, made by a huge company, has a massive gap between the slide and the body.
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  11. #10
    XCR Guru Sean K.'s Avatar
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    Re: Movement in upper and lower

    Quote Originally Posted by JSinAZ View Post
    That is a really interesting idea. I hadn't thought of addressing this at the front of the receiver.
    Sorry JS, I gave you bum info. You cannot use an o-ring on the XCR b/c the upper receiver on the XCR's front "nub" (the piece of aluminum with the hole in it that the front pin slides through) does not have 4 sides to it like an AR. So, there's no way to slip an oring over it. I wonder if you could make a small 3 sided shim of rubber that would go around the 3 sides of the XCR nub and make a compression fit between the upper and lower? That would accomplish the same thing and would need to be probably an 3/32-1/8" thick to do the trick.

    Sorry for throwing out a non-workable idea.

    Sean
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

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