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Hammer not locking back when slide is racked?

Discussion in 'Mossberg 500 Pump Action' started by carlough, Mar 12, 2018.

  1. carlough

    carlough Copper BB

    Messages:
    5
    Sometimes when I rack the slide back to load the 500, the hammer doesn't lock back;/down in the ready to fire position, I'm concerned it will ride the bolt and fire when pumped, and fire when the slide is pushed forward. I'm only have this issue after replacing the trigger pack with a new one (the old one was cracked from the previous owner). Could it be the bar next to the hammer, that points forwards, not being pressed fully down, resulting in the hammer not locking back? If this bar is the problem, other than adding some epoxy to the top of this bar to make it taller, is there any better solution?
  2. Jmm14534

    Jmm14534 .270 WIN Supporter

    Messages:
    181
    Carlough,

    I wouldn't screw with it - sounds dangerous. Call Mossberg service and discuss the issue. If they can't trouble shoot it then send it back to them for service. Their service is very good.
    Last edited: Mar 12, 2018
    John A. likes this.
  3. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    12,980
    Yeah, I wouldn't trust epoxy on that.

    I'd call Mossberg.
  4. CaddmannQ

    CaddmannQ 12g Supporter

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    6,260
    Have you worked on one of these guns before?

    I would carefully compare the new and replacement trigger packs and make sure you have the correct parts.

    You may have a gun made in a year where they changed production over a little bit, so more than one part was used at the time.

    I have a 12ga Ranger like that. It has parts from both earlier and later model guns incorporated into it but it's not the same as either one exactly and I can't find records that it was produced. It's like the gun was built from leftovers and new parts mixed.

    But it's a lot of fun when you pull both triggers at the same time!
  5. carlough

    carlough Copper BB

    Messages:
    5
    I have not loaded it with anything but snap caps since replacing the trigger unit, because I fear the hammer riding the bolt could result in a "slam fire" sort of situation, so although dangerous, I've tried to take appropriate precautions by not using it. The issue is that the trigger doesn't get caught in the locked down position, I know this because when I pull the trigger unit out after racking the slide, it wont be in the "ready to fire" position, and because when this occurs, I can still re-rack the slide. The best explanation I have, is because part 15 (see diagram below) isnt being pressed down fully, I assume this isnt an issue anyone has seen before? As best I can tell, this part has the same specs (to .05 height, yes i measured). Shotgun is a 500A, not sure if that helps. Unfortunately, I'm unsure of the age of the replacement trigger group, but the biggest visible difference is that the new one has all black components, whereas the old one had a shiny metal trigger, if that helps.
    https://www.mcarbo.com/Resources/Mossberg-500-trigger-assembly-diagram.png
  6. CaddmannQ

    CaddmannQ 12g Supporter

    Messages:
    6,260
    Well I would like to test that trigger group in another Mossberg 500 and see if the same thing happens, and if it did I would send it back.

    Was the old one cracked from dropping it on the trigger guard? Any clue? Possible bent pin?
  7. carlough

    carlough Copper BB

    Messages:
    5
    At this rate, I see maverick 88's going for $100 on gunbroker, so it might be better to buy a new one, but might as well look at this one first. The entire body fot he trigger unit was cracked through about a 1/4 inch behind the trigger guard, its very possible that it was dropped on the trigger guard, but I'm not the original owner, so I'm not sure how it was done. I'll take a look at the pin later, you think if its bent it could cause this? I dont recall it looking bent, at least not badly.
  8. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

    Messages:
    12,980
    The sear helps catch the hammer when it' cycled. It's not just the hammer. Again I would call mossberg.
    CaddmannQ likes this.
  9. CaddmannQ

    CaddmannQ 12g Supporter

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    6,260
    Yeah I would definitely contact Mossberg and/or whoever you got that trigger group from.

    If it all went together easy without any fudging of anything, then I would suspect the trigger group is bad.

    I'm just wondering if the gun has been smacked hard enough to deform the receiver slightly at the mounting point. But it sounds to me like you can tell that the trigger groups are different.
  10. carlough

    carlough Copper BB

    Messages:
    5
    I'll probably just strip all the parts out of the new unit, and plop the ones from the old unit in, hopefully that fixes it.
    CaddmannQ likes this.
  11. carlough

    carlough Copper BB

    Messages:
    5
    Good news guys, I found the problem. I got the M-carbo trigger kit, and while installing it, i figured I might as well dissemble and clean the whole thing.... And found the sear spring was snapped in half, and probably doing nothing. I put the one from the cracked unit in, and now the whole thing seems to be working perfectly. So, long story short, the issue was probably the sear spring.
    old mossy, CaddmannQ and John A. like this.
  12. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Forum Moderator

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    Glad you had an extra spring handy. And I'm glad that you were able to fix the problem. Well done indeed.
  13. CaddmannQ

    CaddmannQ 12g Supporter

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    6,260
    Yes indeed. Thank you for the update!
  14. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

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    Glad you found the problem. Thanks for keeping us posted.:)
  15. Jmm14534

    Jmm14534 .270 WIN Supporter

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    Good to hear. Your perseverance paid off. No round trip to Texas for service and no one got killed!!! Great job.

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