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Thread: hammer pin backing out

  1. #1
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    hammer pin backing out

    the pin in my lower reciever that holds the hammer on keeps slightly backing out. its staying in both halves of the frame but..

    1. i dont want to keep adjusting it.
    2. it worries me it may come out enough and snap it when the hammer flies foward from the spring tension


    the pin is snug, and takes a hard push to get it in flush with my reciever but so much as one rack of the bolt and it back out on the left side of my frame. can i just use some thread lock or a tab of superglue?

  2. #2
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    I borrowed this picture from another site. Make sure that your hammer has the retaining spring or "J" spring. This is what keeps the hammer pin form walking. The spring engages a groove in the center of the pin. Check for the J spring and report back.

    You can see it inside the hole...


    -Matt
    Last edited by Quiet-Matt; 09-15-11 at 20:27.
    "Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

  3. #3
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    And they say KNS pins are not functional or necessary!

  4. #4
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    Quote Originally Posted by jet80tv View Post
    And they say KNS pins are not functional or necessary!
    kns pins??

    those the ones were there hoth connected?

    anyways, do i need to pull my hammer out to view that? honeslt, I'm new to owning my own m4, so I have never taken my lower apart..


    *EDIT* screw it, i pulled it apart anyways, looks my hammer has that pin,BUT its not very big, its very little...
    Last edited by KingCobra; 09-15-11 at 20:42.

  5. #5
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    If the spring isn't large enough to engage the groove in the pin properly, it may be where your problems are coming from. While you have the hammer out, re-insert the pin and see if it provides enough tension to stay in. If not I'd look for another hammer.

    -Matt
    "Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

  6. #6
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    On a rare occasion, you might end up with a hammer pin that has an unusually shallow groove cut into it, which does not give the spring much engagement.

  7. #7
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    Quote Originally Posted by Quiet-Matt View Post
    If the spring isn't large enough to engage the groove in the pin properly, it may be where your problems are coming from. While you have the hammer out, re-insert the pin and see if it provides enough tension to stay in. If not I'd look for another hammer.


    -Matt
    Quote Originally Posted by Eric View Post
    On a rare occasion, you might end up with a hammer pin that has an unusually shallow groove cut into it, which does not give the spring much engagement.



    its pretty dang tight. its not wobbling at all, i just had to use a hammer to get the pin back out of the hammer.


    the problem seems to only happen when the hammer is in the rifle..I'll take a picture to show how much the pin is moving out..maybe i'm just paranoid?
    Last edited by KingCobra; 09-15-11 at 22:22.

  8. #8
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    A couple of questions...
    1. Is the pin groove properly centered?
    2. Does this happen to your trigger pin as well?
    My take on it is, it shifts to stick out on one side as a result of the J-spring settling into the groove. Why it does that could either be a pin or lower issue. If it's minimal, I would let it be.

  9. #9
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    Do both your hammer and trigger pins have two sets of grooves so that they may be interchanged? If so try switching them.

  10. #10
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    That's correct because they aren't. You simply replace the worn hammer or pin or whatever the cause is, rather than using a band-aid.

    Properly assembled and quality lower parts rarely fail.

    Quote Originally Posted by jet80tv View Post
    And they say KNS pins are not functional or necessary!



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