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Thread: Failure to extract issues, need help

  1. #1
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    Failure to extract issues, need help

    Some info
    Mac10 - 9mm with sten magazine conversion

    I have the factory upper and it runs great.

    I have a factory type upper that I put together with a 1/2x28 thread barrel so I could shoot suppressed. This upper runs great.

    Fat Ghost upper (using the same bolt used in the 2 other uppers) I get a ton of failure to extract. its always a fresh round wedged into a fired but not extracted round.
    An alignment issue? Bolt face and barrel?
    It does run better when suppressed but still not any where close to acceptable.

    Edit
    Smarter people than I have pointed out that it is more likely a failure to eject. Due to the fact the bolt is moving as it should when fired, if casing did not extract then the bolt wouldn't move.


    Thanks for any advice.
    Last edited by Fulautotank; 09-22-2020 at 10:48 AM.

  2. #2
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    Try cycling 9mm snap caps through.. same bolt & works better With suppression Seems back pressure may be the issue but test cycling would rule out other things. Maybe try a different ammo in it also if you can, just for laughs.
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    Thanks ryebread
    I don't have any snap caps on hand. I'll get some tomorrow and see what happens.

    Ammo I'm shooting is Winchester 124 gr Nato if that matters. I know this is closer to +p loading.

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    Does your factory upper have an extractor grove cut in the barrel? Compare that to the barrel in fat ghost. you can also check to see if the seating depth/chamber Demenssions are the same by inserting a fired case or dummy round into the chamber of both barrels and noting the seating depth.

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    "nklf" beat me to it. My guess would be that the one bolt you have is the original style bolt which requires a notch in the chamber end of the barrel for clearance of the old style extractor. The newer style of extractor does not need the barrel clearance on the chamber end for the extractor. Check the chamber ends of the older uppers that run compared to the Fat ghost.

    Scott

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    I “herd” You can notch a barrel Just by smashing it with a rock

    No really- don’t do that!
    Live BRAVE, Live FREE!

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    None of the uppers have the notched chamber. I think I can rule that out.

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    Maybe just the chamber is a little tight, could that cause this?

  9. #9
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    When you get your malfunction, is the fired casing still in the chamber or is it floating around loose in the action getting in the way?

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    Is it a new style bolt or an old style bolt?

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    Fired round is still in the chamber.

    Not sure what the difference is between new and old style bolts.

  12. #12
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    OK, you need to bear in mind that in a straight blowback action like the MAC, the extractor doesn't pull the fired casing out of the chamber- the casing is violently blown to the rear by the pressure in the chamber and drives the bolt to the rear also. If the casing winds up back in the chamber and there's a live round trying to get in there also, that tells you a couple of things. One, the bolt is being driven back far enough to pick up a round from the magazine (which is good). Two, the ejector is not hitting the fired casing (which is bad). If the ejector was hitting the casing, it would be knocked out of the bolt face and couldn't possibly wind up back in the chamber. If it wound up floating around in the action, that would point to the extractor not providing a pivot point for the casing to rotate against and be properly ejected, but with the fired casing being replaced in the chamber, the culprit is probably the ejector.

    Check to be sure the ejector is there and is emerging from the bolt face before the bolt face gets past the rear of the magazine as you look in the ejection port and hand-cycle the bolt.

    The old-style extractors protrude slightly from the bolt face and will smash into the back of the barrel is a relief cut is not provided. The newer ones are slightly below flush and don't need the cut.

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    When I cycle the bolt by hand I see the ejector rod when the bolt face is almost half way over magazine (the middle of the mag)

    I never thought about the casing coming all the way back with the bolt and then going back into the chamber. When I have the malfunction the fired round is fully seated in chamber and the new unfired round is pushed directly into the rear or just above the still chambered casing.

    That makes me believe the fired round/empty casing is not being extracted. Of Course I have been proven wrong once or twice before.

  14. #14
    Registered User DINK's Avatar
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    OK, if the casing doesn't come out of the chamber, what is pushing the bolt to the rear?

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    I appreciate all the help guys. I think that I will clean and polish the chamber and see if there is something that may be causing the casing to stick into the chamber. If I remember correctly it runs a little better when the barrel is freshly cleaned.

    I will also try a different type of ammo. I was getting a good deal on the Winchester 124 gr Nato so been shooting mostly that. I did shoot some 147 gr. flat nose American Eagle and that did not want to run at all.

    Also going go pick up the snap caps today and do some testing with those.

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    DINK
    That makes three times I've been proven wrong. You definitely have a good point there.

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    Maybe putting in a new ejector rod will help. I should have one laying around. Can't hurt I guess

    Thanks DINK

    I'm getting closer to solving it.

  18. #18
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    I have no interest in proving anything- just helping you out. I bought my first MAC in 1982 so I've been playing with them for a long time. Personally, I like the ejector to be long enough to just let a live round clear the back of the barrel as it pivots outward, but some situations require it to be shorter.

    Yank the ejector rod out and roll it across a flat surface to make sure it isn't bent slightly. That can cause binding and keep the bolt from recoiling properly.

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    I was making an attempt at being funny so please don't think I was being a smart ass.
    I really do appreciate your help.
    You got me closer to figuring this out. I was totally off base with my initial assumption of failure to extract.

    Could feed angle of the magazine be a problem? To much feed angle and maybe front of round at top of magazine contacting rear of fired casing during bolt travel?

    I do have a bunch of sten mags and the angle varies a lot.

    I guess that shouldn't happen with the rear of the casing still in bolt face. Just throwing stuff out there.
    Last edited by Fulautotank; 09-22-2020 at 11:24 AM.

  20. #20
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    I put in new ejector rod. The hole that the rod travels through on the bolt had a little junk in there. Had to clean it to get ejector rod to travel smoothly.

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