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Thread: Diagnosis check...bolt speed?

  1. #11
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    Quote Originally Posted by MK18Pilot View Post
    PSA + Gun Show = Junk

    Why do you want to stamp your name on a woodshed build? I hope your getting paid handsomely...



    Completely irrelevant...
    My name isn't on the build...I was just trying to help them get it running.
    Semper Paratus Certified AR15 Armorer

  2. #12
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    Quote Originally Posted by djegators View Post
    Did you say what ammo they were using?
    PMC Bronze 55gr
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  3. #13
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    Quote Originally Posted by MK18Pilot View Post
    Given a serviceable magazine, the bolt group can't outrun it, period. This is one of those nagging errornet theories that just won't die.
    A super worn out buffer spring (along with a CAR buffer) can cause bolt over run IMHO.



    C4

  4. #14
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    What else would explain the bolt returning without picking up a new round? Unless someone can prove otherwise, I'm not convinced its out of the realm of possibility.

    Quote Originally Posted by MK18Pilot View Post
    Given a serviceable magazine, the bolt group can't outrun it, period. This is one of those nagging errornet theories that just won't die.
    B.A.S. Mechanical Engineering Technology

  5. #15
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    Quote Originally Posted by C4IGrant View Post
    A super worn out buffer spring (along with a CAR buffer) can cause bolt over run IMHO.



    C4
    A pretty smart AR guy once told me that "a malfunction that can't be intentionally induced can't happen".

    I would understand this to mean that we should be able to take an otherwise reliable carbine, install bad parts in it, and in this case get it to consistently object to completing the cycle of operation by giving us a bolt over base malfunction. That being said, I've never seen anyone who could intentionally induce the malfunction.

    Its been my experience that weapons that consistently exhibit bolt over base malfunctions are a result of unserviceable magazines, rifle barrel extensions in carbine upper receivers or an out of spec lower receiver. Every now and them the stars align and a BOB malfunction will occur. We all now the drill from there... take cover and perform a remedial action drill and get back in the fight.

  6. #16
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    Quote Originally Posted by MK18Pilot View Post
    A pretty smart AR guy once told me that "a malfunction that can't be intentionally induced can't happen".

    I would understand this to mean that we should be able to take an otherwise reliable carbine, install bad parts in it, and in this case get it to consistently object to completing the cycle of operation by giving us a bolt over base malfunction. That being said, I've never seen anyone who could intentionally induce the malfunction.

    Its been my experience that weapons that consistently exhibit bolt over base malfunctions are a result of unserviceable magazines, rifle barrel extensions in carbine upper receivers or an out of spec lower receiver. Every now and them the stars align and a BOB malfunction will occur. We all now the drill from there... take cover and perform a remedial action drill and get back in the fight.

    Ever cut springs down on Mags or buffer springs??? I can make it happen and have seen it occur in the wild.

    With that said, it HAS to be bad in order to get it to happen so it is not common.


    C4

  7. #17
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    Quote Originally Posted by C4IGrant View Post
    Ever cut springs down on Mags or buffer springs??? I can make it happen and have seen it occur in the wild.

    With that said, it HAS to be bad in order to get it to happen so it is not common.


    C4
    Cats got my tongue...

  8. #18
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    Well, if the gent and his son return next week, I'll throw their PSA upper on my DD lower and see if it runs. That'll rule out an out of spec lower if I still have malfunctions and either prove or dis-prove the bolt-outrun issue.

    I did manage to get it to fire three rounds in a row, though, so if it's an out of spec lower issue, the stars must have somehow aligned with the angle of the magazine, etc.
    Semper Paratus Certified AR15 Armorer

  9. #19
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    Re: Diagnosis check...bolt speed?

    Personally, it sounds under or severely over gassed. I have had overrides. It came from running dirty and really hard, short stroking.

    The reason I asked earlier about brass is because where that first brass lands before jamming up could lead to your culprit. Under-gassed with too much bcg weight or too heavy buffer, or too weak spring (short stroking). Or over gassed, too light buffer, or wrong spring. Most guns can be tuned properly by changing out components to create a balance.

  10. #20
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    Quote Originally Posted by TactTeam View Post
    Where are the casings ejecting? 12 o'clock being the muzzle and 6 o'clock being the stock?
    Quote Originally Posted by MK18Pilot View Post

    Completely irrelevant...
    IMO, Ejection angle is totally relevant.

    That in combination with a lockback test, helps narrow down an over gassed/under gassed condition.

    If the gas port turns out to be rifle sized, a CustomTune Gas Port can bring it back down to the .060" that it should be.
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    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
    BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

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