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M-16 Sear question

Discussion in 'NFA & Class III Discussion' started by stewball, Feb 2, 2010.

  1. stewball

    stewball Sharpshooter

    Likes Received:
    Dec 9, 2008
    Ok, I'm going to have to display my ignorance, but I'm sure one of you Class III guys can help me out. I recently bought a 22 upper (Spike's) with the auto trip installed. My question is this: In the full auto position does the hammer on this weapon engage the sear momentarily on the return travel of the BCG, then releases itself to strike the firing pin or does it simply travel along with the bolt with enough inertia to complete the firing sequence? On a 22 upper "auto trip" mechanism, is the part of the sear that is pushed forward by the BCG on a normal type bolt supposed to hold that part of the sear forward to allow for full auto fire? Any explanation of this would sure help my understanding of how this works.

    Thanks much

  2. CAR-AR-M16

    CAR-AR-M16 Sharpshooter

    Likes Received:
    Sep 6, 2005
    The auto sear is in the lower receiver (see pic below) and it holds the hammer back until the bolt just closes. The sear trip that came with your .22 kit is designed to do exactly what it is named, it trips the auto sear. The bottom portion of the auto sear catches and holds the hook on the hammer until the bolt just closes. At that point the sear trip (or the portion of the M16 bolt carrier in a 5.56 rifle) pushes forward on the top of the auto sear which pivots the bottom portion of the auto sear away from the hammer hook and allows the hammer to fall. In a semi auto rifle the sear trip does nothing since there is no auto sear to trip. Hope that helps.


    You can see the hook portion of the M16 hammer in the pic below (it is the portion sticking out at the top right of the M16 hammer).

    [Broken External Image]

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