JM Pro 930 not firering

Discussion in 'Firearm Maintenance, Safety And Troubleshooting' started by David Moore Williams, Apr 18, 2017.

  1. David Moore Williams

    David Moore Williams Copper BB

    Messages:
    6
    Hi everyone, new to this forum. Hope someone can help. I have a JM Pro 930 Tactical series 12g. here is my issue.
    The first shell loads and fires. The second loads, I can hear the hammer drop but no ignition. No fireing pin mark on shell. I can hand rack the next shell in, it will fire but the next one loads and nothing but hammer drop. Alternating ignition of rounds.
  2. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    158
    It sounds like your gun isn't going fully back into battery between shots. It may appear that the bolt is fully forward, but if the slide (bolt carrier) under it doesn't return fully forward and push the gas piston back in place, the bolt lug doesn't lock into the barrel hood and blocks the firing pin. It could be a number of things causing it, but depending on round count it is most likely the piston and rings need detail cleaned. How many rounds are through the gun?

    Also, check out the Mossberg 930 specific section of the forum and you'll get a lot more information about the 930 itself.

    William

    http://www.OR3GUN.com
  3. OhioArcher

    OhioArcher Where's da fishes? Forum Moderator Supporter "Philanthropist"

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    3,726
    Let us know what ammo you're using. Sometimes these things a finicky eaters...
  4. David Moore Williams

    David Moore Williams Copper BB

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    6
    William,
    thanks for your quick response.
    Funny you should be the one with information, I was just on your website trying to decide which of the combo kits I needed to buy for 3gun.....
    I just bought the gun used. $450. with carbon fiber stock and grip. grey ceracote finish. I have no idea how much it was shot. doesn't look like much wear on the bolt surface.
    I was shooting the cheapest Herters 1oz 71/2. light load. Your adjustable spring perch might help with light loads..?
    I will start with a good tear down and deep clean. but....if I am doing that I should probably buy your Pro competition combo so I only have to do this once.
    You guys have any promotional coupons for a Manwife with six kids shooting 3gun.........:)
    I would love to pimp your stuff all over the Montana areas.

    did you go to the Nationals in Vegas last week ? If so, how did you guys do. I had a bunch of shooting buddies there and they posted some great videos of some awesome stages.
    thanks for your help.

    David Williams
  5. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    158
    We had a couple of shooters there running our parts and logo, but we didn't make it ourselves. If you check our Facebook page, they usually give us a shout out linked from somewhere. (Can you tell that social media isn't my forte?)

    As to your specific gun, the word 'Cerakote' combined with the word 'used' always sends up a bit of a red flag. It is not uncommon for an inexperienced Cerakote applicator to turn a gas shotgun into a single shot by coating the wrong parts. When you tear it down, ensure that the following parts have not been finished with Cerakote:

    Magazine tube
    Piston (or rings)
    Cylinder (in barrel, where the piston lives)
    Receiver rails
    Bolt
    Slide (Bolt carrier)

    Cerakote is a great external finish, but it does add to tolerances on moving parts. It also wears against itself quite easily and combined with lube creates a gritty mess of friction at contact points until it wears completely away. If your gun is Cerakoted on any of the above surfaces we will need to address the severity and best way to work around it.

    If your gun is free of excess Cerakote, the MST and CSP (possibly ASR too) are the places to focus on for improved cycling of light loads. A 1 oz, #7.5 is about the bottom end of what a factory 930 is expected to cycle. If you stay away from hot slugs and buckshot, getting those lighter to run reliably should be easy.

    If you order a Combo from us, mention that you started this thread at MossbergOwners and we'll make sure at least one of your kids can keep their head warm.

    ;)

    William

    http://www.OR3GUN.com
  6. David Moore Williams

    David Moore Williams Copper BB

    Messages:
    6
    Thanks William,

    the Cerakote issue might just be the problem. I will tear down and inspect all those aforementioned pieces.
    love the facebook page.
    before I invest any more I want to make sure its going to worth investing in.

    'Thanks for you help. hope to see you out there sometime.
    I"ll let you know what I find.

    David.
  7. David Moore Williams

    David Moore Williams Copper BB

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    6
    for anyone interested in this thread here is a good cleaning video. I love Jerry M.
  8. David Moore Williams

    David Moore Williams Copper BB

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    6
    or of course.........the best one
  9. Bobster

    Bobster .308 Supporter

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    1,304
    And who but Jerry to show you the care and feeding of his namesake shotty! :)

    Thanks for posting David, and Welcome Aboard! :)
    David Moore Williams likes this.
  10. David Moore Williams

    David Moore Williams Copper BB

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    6
    OMG................
    My gun was so mucked up.....even those videos were not enough information to do the complete job.
    Piston was gummed, the overload springs above the piston were gummed. the shell plug would not even move in the magazine. bolt was sticking in the barrel.
    I had to disassemble, hone and polish every single part on the gun.
    These things are way over engineered and really rough finished compared to my Benelli.
    Runs smooth as silk now. I love it. great trigger and fast..!!
    Might make this my open gun of choice. whos extended mag should I use. does anyone make a +9 or 10.
    Is the OR3Gun open gun all in house parts../ who makes the speed loader funnel, Arrendo.?
    Thanks for all you help William.

    You will see an order from me soon. after opening up the loading port I really need to get the foregrip out of the way.

    so Happy,'

    David
  11. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    158
    Glad you got it some much needed maintenance. Sometimes it seems people sell them when they need cleaned rather than just clean them.

    Everything but the speedloader bracket on our house gun is ours. Arredondo makes the speed loader bracket. We are a dealer for them now and will be selling their brackets anodized in Pitch Black and Marine Blue to go with our parts soon.

    Nordic Components makes the most modular extension tubes for the 930. You end up buying a nut and tube separately, but they make all sizes from +1 through +9. The +8 is a popular choice for Open. You can load 3 of the 4-round speedloaders or 2 of the 6-round and be at capacity. Any more than that can be tough to maneuver on some tight stages.

    William

    http://www.OR3GUN.com

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