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Help... Takedown pin will not seat completely

Discussion in 'Black Rifle Forum' started by Briley9, Apr 2, 2010.

  1. Briley9

    Briley9

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    Just got a used car upper, and the takedown pin will not seat completely (won't clear the left side) on a Mega lower. The pivot pin was snug, but seated correctly. The TD pin was also very snug going thru the upper receiver TD lug. Looks like approx 1/32" top of pin is hitting the lower receiver TD pin hole at 12 o'clock.

    I've tried this upper on a RRA lower and it had the same 12 o'clock TD pin issue... both RRA and Mega are complete rifles, and have no issues swapping uppers - 4 different uppers. So, pretty sure the issue is with this upper.

    Got couple questions: in case there's a quick fix, before I try to get relief from the seller.

    1. short of replacing the upper receiver, has anyone seen this and have a solution to remedy the out of spec upper?

    2. aside from the TD pin not seating completely, all function tests passed.

    3 would it be safe to test fire 10rds for grouping to see how accurate the barrel is? before I replace the upper, as a last resort...

    Thx...
     
    Last edited: Apr 6, 2010
  2. WayaX

    WayaX Lifetime Member

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    The roll mark on the upper is Anchor Harvey. That's all I can tell you.
     

  3. Kentak

    Kentak

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    Just to be clear--

    When the upper is pivoted up, the TD pin goes all the way through as it should? And, do I understand you to say putting a different upper on this lower makes the issue go away?
     
  4. faawrenchbndr

    faawrenchbndr CLM

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    Unless you open the upper receiver's lug hole,(not recommended).......you need a new upper receiver.
     
  5. rjrivero

    rjrivero

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    If it works with other uppers, the I agree that the upper on that 18" barrel is out of spec.
     
  6. Briley9

    Briley9

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    Yes, this lower has had 4 different uppers on it in the past year, with no issues.

    uppers = RRA, Stag, Bushmaster, & LMT...
     
  7. lawman800

    lawman800 Juris Glocktor

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    It just keeps getting better, don't it?
    Check to see if there is an Accu-wedge. Sometimes that gets stuck in the way. Also, it's easier if the hammer is cocked back, so I have been told.
     
  8. Briley9

    Briley9

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    no accu-wedge... and the hammer is cocked - no external pressure on the receiver(s).

    Thx
     
  9. Kentak

    Kentak

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    Given what you have told us, it sounds like an out of spec upper. That sucks, man.
     
  10. Kentak

    Kentak

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    If this was me, I might try to find a gunsmith who understands the issue and have him modify the TD pin hole in the upper just enough to make it work. It wouldn't even have to be a gunsmith, a competent machinist should be able to handle this.

    This is fixable, take heart.

    I would think the cost should be reasonable.
     
    Last edited: Apr 3, 2010
  11. g21owner

    g21owner

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  12. faawrenchbndr

    faawrenchbndr CLM

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    This idea will permanantly ruin this upper. Breaking through the hard coat annodizing will drastically weaken the upper receiver's lug.
    Steel pin, aluminum hole,.......bad idea.

    This is even a worse idea,.......risk stress cracking either receiver?
    Not worth messing with, when a upper receiver can be replaced for less than$100
     
  13. ncvarmint

    ncvarmint

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    Just done mine, and it was tight, a M&P lower with a bcm upper, had to tap it with a hammer, and it went in, it should loosen up i hope

    trevor
     
  14. lawman800

    lawman800 Juris Glocktor

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    It just keeps getting better, don't it?
    My friend had a particularly tight DMPS upper and he had to dremel out the hole for the rear pin. Didn't take much but just a smidge of a mm will cause it not to seat.
     
  15. Kentak

    Kentak

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    Drastically weaken? How so? The anodizing of the aluminum is done for surface protection, not structural strength. The strength comes from the alloying of the aluminum. I'm certainly not talking about removing structurally significant amounts of metal. From his description of the problem, it's possible that a little polishing of the hole in the right direction might do it.

    I think you're very much overstating the risk of galvanic corrosion. I'd worry about it if the gun was stored in a salt water bath. The point being, an electrolyte must be present. Certainly, most of us don't allow our weapons to stay wet any longer than necessary, and the OP is probably no exception. Just keep a little grease on the pin.