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Thread: New build double fires then no hammer reset

  1. #1
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    New build double fires then no hammer reset

    Hi all. I recently built an AR for a friend. I've built six different rifles with no issues though in my own builds I'm very aware of the "buy cheap buy twice" mantra.

    My buddy spent a lot of money on some parts, then underspent on others. Specifically, he bought a kit that included buffer tube, spring, buffer, stock.

    The weights inside the buffer slide when you tip it. I suspect this may be causing some sort of bump fire situation. It shoots two rounds, cycles and goes into full battery, but doesn't reset the hammer. Any ideas? I haven't thrown a good buffer in there yet but any other input would be great.

  2. #2
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    What excatly do you mean by "dosen't reset the hammer"?

    I would check/replace the FCG before the buffer.

  3. #3
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    Ithe gun fires twice, goes into battery with a new cartridge in the chamber, but the hammer stays un-cocked after that two round burst. Everything is ready to fire but the hammer.

    What should I be looking for in the FCG? Everything is brand new?
    Last edited by jafount; 10-12-10 at 15:04.

  4. #4
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    Amount of disconnector engagement and the strength of the disconnector spring. What trigger? Any engagement or over travel adjustments on it>
    Last edited by az doug; 10-12-10 at 15:22.

  5. #5
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    Quote Originally Posted by az doug View Post
    Amount of disconnector engagement and the strength of the disconnector spring. What trigger? Any engagement or over travel adjustments on it>
    It's a standard FCG included with DPMS LPK.

  6. #6
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    List of things I would look at:

    1. springs, are they installed correctly (all of them)
    2. does it look like any of the edges are rolled/have a lip in the hammer/disconetor area.
    3. are the pins installed correctly.
    4. suppect that it was made incorrectly

    this is a good start for mil-spec trigger that I use. Somebody with a lot more experence please correct if I am wrong/point this guy in the right direction.
    Last edited by jbsmwd; 10-12-10 at 15:29. Reason: found out the type trigger

  7. #7
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    Quote Originally Posted by jafount View Post
    It's a standard FCG included with DPMS LPK.
    I found the problem!

  8. #8
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    The disconnector is not holding the hammer until the trigger is reset, or the time between the disconnector releasing the hammer and the sear engaging it is too great. Also check the amount of spring tension on the disconnector.

  9. #9
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    This typically occurs from either improper assembly or a defective fire control part(s). First check that the disconnector spring is installed and has the wide end down. Next things to check and/or replace would be the disconnector, hammer, trigger. Also be sure one of the hammer/trigger pins did not break or slide out of place.

    My guess is that it does not pass a function check as is...specifically checking for disconnector function. With the unloaded gun on fire, point in a safe direction, pull the trigger and hold the trigger back while cocking the hammer. Very slowly let the trigger creep forward. There should be a distinct thud as the disconnector releases the hammer and the hammer engages and is retained by the trigger. If the hammer goes forward without transferring to the trigger, that is a bad thing and would result in a round going off. This is often referred to as fire on release. One round is fired when the trigger is pulled and a second when the trigger is released.

    That weapon needs to be taken out of service until it is repaired.

  10. #10
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    Take the upper off of the lower assembly and do a thorough function check of the FCG for proper operation and then let us know what you find.

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