9mm upper breaking bolt catch's

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    C

    Chevyman85

    Active Member
    Feb 14, 2013
    468
    DoCo
    I've got a CMMG 9mm WASP upper that has broken 2 CMMG bolt catch's both times I've shot it. The break occurs between the first and second mag shot. It's either when the catch engages after the first mag or when I hit the bolt release to chamber the first round from the second mag.

    I've got a 9mm buffer installed. Do I also need a lighter spring? Whos's had this problem and how'd you fix it?
     
    mch28

    mch28

    Active Member
    Sep 20, 2007
    451
    You can put in one of these spacers or make one (like I did). Some people just put in a few quarters (I think 8-10) behind the spring. The problem is that the bolt gets too much inertia traveling all the way back and then coming forward breaking off the catch. The idea is to allow the bolt to come back just far enough for the bolt catch to hold it. http://www.spikestactical.com/new/z/lower-parts-spikes-st9bs-buffer-spacer-9mm-p-174.html
    SLA09BS.jpg
     
    C

    Chevyman85

    Active Member
    Feb 14, 2013
    468
    DoCo
    When I pull the charging handel back there's only just enough "extra" space for the bolt to clear the catch. I'm not sure a spacer will fit unless the bolt moves farther back then I'm seeing.
     
    mch28

    mch28

    Active Member
    Sep 20, 2007
    451
    Is your 9mm buffer the same length as a carbine buffer or is it a longer version? Standard carbine buffer is about 3.25". Try pulling back the charging handle then push rearward on the bolt to see if it goes any farther than how far back the charging handle pulls it.
     
    C

    Chevyman85

    Active Member
    Feb 14, 2013
    468
    DoCo
    I have the Spike's SS 9mm buffer, about an inch longer than a carbine buffer. After checking the bolt again, it will not go back any farther than what the charging handle brings it back. Just enough to clear the bolt catch, maybe "1/16.

    Could there be an issue with the spring?
    Is there a 9mm buffer spring that should be used?
    Could there be a problem specifically with the CMMG bolt catch or the Spike's SS 9mm buffer?
     
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