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Thread: Please help me diagnose this junk!

  1. #1
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    Please help me diagnose this junk!

    So a friend of mine gave me his PSA "Dissy" style upper that he purchased against my advice. It doesnt run.

    So initially I thought it might have an out of spec chamber that was causing 5.56 casings to stick as the owner told me that it runs better (but far from perfect) with .223 cased ammo. I used one of Ned's chamber gauges which confirmed that the chamber was indeed tight. I ran one of Ned's ingenious reamers thru it and it definately removed some material from the chamber

    After running a few mags of different ammo through it today to see what was up, it was still suffering from some odd (to me) double feed/failure to eject/Im not sure malfunctions. So the out of spec chamber obviously is not the only issue with this thing.

    I tried to take a video of the cycling but I picked the wrong resolution on my phone so it is a bit grainy http://www.youtube.com/watch?v=cgAGrmp_SIc

    Heres a couple of pics of the stoppage:




    Please, no comments the Zombie theme crap

    Anyway, it appears that the fired casing is being held by the extractor claw all the way to the back of the ejection port and being ripped away by impacting the rearmost area of the port. Not positive about this but every casing fired from it has the same score mark mid casing. Most of the casing that actually eject are going almost straight forward after striking the back of the ejection port.

    Any help is greatly appreciated as at this point all I can confirm is that this PSA upper is a bonifide P.O.S.
    "The future's uncertain, and the end is always near." Jim Morrison

    "Fortuitous outcomes reinforce poor training and tactics"

  2. #2
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    How many rounds has been through this rifle,approximately?
    What weight buffer is being used?
    Is the ejector sticking?

    The brass that is leaving the port is beating the deflector all over the place!
    " If i cannot be a good example Lord, let me be a terrible warning"

  3. #3
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    I would change the ejector and spring inside the bolt and start form there. After that, diagnose the buffer and recoil spring. If it is a middy gas system, make sure it does not have an o ring on the extractor.
    "Perfect Practice Makes Perfect"
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  4. #4
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    Quote Originally Posted by uncle money bags View Post
    How many rounds has been through this rifle,approximately?
    What weight buffer is being used?
    Is the ejector sticking?

    The brass that is leaving the port is beating the deflector all over the place!
    Approx 200rds

    "H" buffer

    No, the ejector does not stick and the spring tension feels normal
    Last edited by nickdrak; 09-20-12 at 02:31.
    "The future's uncertain, and the end is always near." Jim Morrison

    "Fortuitous outcomes reinforce poor training and tactics"

  5. #5
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    Is it really overgassed?

    223 ammo is lower pressure and tends to run better in overgassed setups.

    If cases are hitting the rear of the ejection port rather than the deflector, they can bounce straight forwards.

    Is their dissy a mid gas with rifle hand guards ?
    Last edited by Clint; 09-20-12 at 03:21.
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  6. #6
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    I know what the problem is! It says "ZOMBIE KILLER" on it. Sorry, couldn't help myself.

    Ok, simple things first:

    1. Clean (scrub) everything (chamber, bolt, etc). Properly lube after.
    2. Get a KNOWN good mag.
    3. Get good ammo (nothing steel, nothing XM, etc).
    4. Pull extractor out of of bolt. Make sure there is nothing inside the bolt and that it has proper spring tension when in stalled. The claw on the extractor should be sharp to the touch.
    5. Look closely at the ejector. Make sure it has full range of motion (no grinding or slow movement).


    Function testing:

    1. Load one round into mag and chamber it.
    2. Fire round. Did it lock to the rear?
    3. Assuming it passed the above, load two rounds and see what you get.
    4. Continue on till you get a stoppage. If it looks like the one in the pic, I would go back and ream the chamber again. Clean and re-try.



    It is hard to troubleshoot a problem via the net so if you still don't get anywhere, send it to me to look at (as I like problem children).



    C4

  7. #7
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    Put a bolt carrier group from a known good running in it and see what happens.

    I'd start off with a new extractor spring, insert and ejector spring.

  8. #8
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    To me the second pic gives the problem away: there is another round stripped from the magazine and loaded into the chamber. That rules out a gas/buffer/action spring issue.

    I'd bet if you drop another BCG in it the problem goes away. Bad Ejector is my guess. Yes I know you said it feels fine, but it's obviously not working properly. Swap to a known good BCG and see how it runs.
    Semper Paratus Certified AR15 Armorer

  9. #9
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    What did PSA have to say about it?
    Steve

  10. #10
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    This was happening to my BCM not long ago, mine was remanuf. Ammo that was loaded to hot.
    Quote Originally Posted by C4IGrant View Post
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    This is 2012. The world is going to end this December and people are still trying to debate the merits of piece of shit, cost cutting crap AR's. Really?

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