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m11-9 firing bursts rather than full auto

Discussion in 'NFA Firearms and Accessories' started by 1KPerDay, Jul 7, 2019.

  1. 1KPerDay

    1KPerDay Member

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    What should I check first? I had some new shooters try it out yesterday and it was actually good because it would only fire 3 or 4 round bursts, or the occasional single, even with the trigger held back. I thought maybe it was newbies milking the trigger but I fired it after they left and I got about a 6 round burst, then I was able to empty the mag. But something ain't right.

    Mine is a Cobray/SWD. where do I get parts and what do I buy?

    Thanks
     
  2. jmorris

    jmorris Member

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    Assuming they chambered, what did the impression on the primer look like?

    Were you using reloads or factory rounds?
     
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  3. entropy

    entropy Member

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    Time to replace springs. Recoil spring and sear spring for sure. Numrich is out of both, I'd try Sarco, Ahlmans, Jack first, etc.
     
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  4. 1KPerDay

    1KPerDay Member

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    Okay thanks. To be clear, every round that the bolt closed on fired and extracted. The sear or whatever was intermittently stopping the bolt as if releasing the trigger. Every primer looked fine and it was factory S&B ball.
     
  5. AK103K

    AK103K Member

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    This may sound silly, but have given it a good cleaning and flushed things out real well?

    Theres no primers, or any other junk stuck down in there anywhere?

    I used to regularly find empty cases in the tube behind the bolt on my M11/9mm. Never could figure out how they got in there, but there they were. Strange things can happen.

    How many rounds do you have through it?

    Hows the buffer look? Is it tore up? If so, whered all that junk go?

    If you need parts, might try here.....

    http://www.cobray.com/smg-and-obs-parts-b-list.aspx

    A couple of others popped up in a search.
     
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  6. 1KPerDay

    1KPerDay Member

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    Doesn't sound silly at all. I had it apart a few hundred rounds ago when I swapped out the 22 conversion. I'll clean it out again and have a look. Thanks for the reminder.

    Not too many hundreds of rounds through it at this point... I could never get the zytel mags to run properly and I've only shot it about 3 times since I got some good ones, maybe a couple thousand rounds max if not less. It appears to be in very good shape. I bought it new.
     
  7. AK103K

    AK103K Member

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    I bought mine new from Cobray in 85. Paid $225 for it. :)

    Shot a bazillion rounds through it over the years too. Only trouble I had with it, was shooting about 2000 rounds of HOT Spanish SMG ammo not long after I got it. That sheared off the charging knob, and cracked the upper in a couple of places. Ran like an SOB on it though. :D

    If you took it apart, maybe something didnt get back together right? It happens.
     
  8. 1KPerDay

    1KPerDay Member

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    I didn't disassemble it... just field stripped. And the last time I shot it it worked perfectly. My original charging knob/disc thing broke off too, and I've never run super hot ammo in it so i wonder if there was an issue with that part LOL
     
  9. AK103K

    AK103K Member

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    Does it shoot OK in semi? Might be a clue there.

    I dont know if the charging knob is a flaw or not. The one I replaced it with, lasted another 30 years or so without issue. As did the upper I replaced.


    Do you have the Zytel mags with the staple at the top? Or are they the old style?

    Also, are the fronts blown out right at the top from rounds being driven through them?

    All my mags were the later Zytel. They all had the fronts blown out, and they all worked fine. I had a couple of the older ones early on, and they split at the back. Thats the reason for the staple.

    Back in the 90's, someone came out with some steel mags for them, that were supposed to be better than the Zytel. Of the batch of 10 got, only one would fit in the mag well, and the one that did, didnt work.
     
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  10. 1KPerDay

    1KPerDay Member

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    My zytels don't have any staples. I only keep them out of sentimental value as they don't work as mags. Converted PAM mags sold by Jerry Prasser of Recon Ordinance are awesome if he's still making them FYI. If you still have your gun.
     
  11. 1KPerDay

    1KPerDay Member

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    I just looked at it again and hosed the lower out. Nothing obviously broken or missing but I'm ashamed to say I don't know how to take it completely apart. The buffer is a little worn but intact. No bits of anything I can see impeding function. Works fine in semi, still fires 2-5 round bursts in full. Safety functions. Tried 3 different mags, same results.
     
  12. AK103K

    AK103K Member

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    I got rid of mine a number of years back now. Turned it into a couple of suppressors, some accessories and the tax on them.

    I seem to remember that when you rotate the selector from semi to full, you can see things (Im assuming the disconnector is involved there) cam down, and out of the way. Its been awhile, but I do remember that going on. In full, the trigger simply drops the sear and holds it down, as long as youre holding it and the bolt continues to cycle.

    Maybe put it on semi and see whats going on, and then do the same, and see what might be moving that is getting in the way of the bolt as it travels. They really arent that complex, I would think youd see or feel something moving around if it was broken.

    Is the selector tight and deliberate to move? Its not moving around under recoil and bouncing it into semi?

    You know its probably going to be something stupid when you do find it. :D
     
  13. 1KPerDay

    1KPerDay Member

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    No it's not moving. I'll keep looking. Thanks for the help
     
  14. GarrettJ

    GarrettJ Member

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    Your issue is actually not all that uncommon. It comes from a weak spring under (I believe) the disconnector. You can change it out (I’d do all of the trigger group springs while you’re at it), and it should take care of it.

    The other solution is to just remove the semi auto trip altogether. The gun will then be a full-auto-only. Which doesn’t bother many people. I still have mine, as it continues working fine.

    Helpful tip: take a picture of your trigger group before taking anything apart. It really helps when you go to reassemble.

    Also, the hockey puck charging Knob breaking off is another known issue. It fatigues and just lets go, usually beaning the shooter in the forehead.

    There are a handful of side-cocking upper options on the market. They take care of the cocking knob issue, and usually have better ergonomics anyway.
     
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  15. 1KPerDay

    1KPerDay Member

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    Thank you. I don't have any problem with a FA only... that's kinda the point. but I'll try sourcing and replacing the spring.
     
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