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Mossberg 930 partial failure to chamber

Discussion in 'Firearm Maintenance, Safety And Troubleshooting' started by Borsy14, Aug 29, 2018.

  1. Borsy14

    Borsy14 Copper BB

    Hey everybody, first post, but a long time Mossberg user. I finally stepped up to a 930 semi-auto after shooting Mossberg pumps for many years, but out of the box I'm having issues with the gun.

    I got the gun home last week and cleaned off all the packing grease. I oiled it back up a bit and went out to shoot. Right away the gun was having trouble fully chambering rounds both 2.75 and 3" shells. Its like they were getting caught as they were just entering the chamber. They would get caught either when dropping the round in the chamber and hitting the bolt release, and, at other times, from a shell coming from the magazine tube. Needless to say, I'm pretty let down by the gun right now.

    I recleaned the gun and lubed the inside of the receiver/chamber with a generous amount of CLP. While running wet, there was not a single issue with chambering rounds until I wiped/dried off the CLP and the issue returned.

    One photo is of a snap cap that didn't chamber properly just like the various shells I was shooting. The second photo is of the chamber. I suspect a rough chamber, sharp chamber lip, or rough shell lifter, but I really have no idea.
    Any thoughts or questions are much appreciated. Should I send it back to Mossberg? Help!

    Attached Files:

  2. John A.

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

    How does the chamber feel to your finger? That's usually one of the first steps when you suspect a rough chamber. If you have a dental pick, stick it up in there to the end of the chamber and rub it along the chamber as you pull it out of there. If there are any imperfections, the dental pick will snag and drag on them.
  3. Borsy14

    Borsy14 Copper BB

    Hey John, thanks for the response. It feels a bit rough, but its not really any more rough than any of my mossberg pumps, but maybe the 930 is more sensitive to a rough chamber?
  4. OR3GUN

    OR3GUN Sponsor Sponsor

    The 930, like any autoloader, is more sensitive to a rough chamber than a pump. The gas system creates the cycling force to chamber and extract each round in an auto, where your hand (and whatever force is required) is responsible for the process with a pump. Your 'variable elbow grease system' is sometimes more reliable with finicky shells.

    Somewhere here there are instructions for chamber polishing posted. I'll see if I can beat someone else to digging them up for you.

    Welcome to the forum!


  5. Scoop

    Scoop .30-06

  6. meanstreak

    meanstreak .30-06 Supporter

    Borsy, welcome to the forum. I hope your new gun is an easy fix. It sucks when a new gun has issues.
  7. Borsy14

    Borsy14 Copper BB

    Thank you for the suggestions and info guys. I'm tempted to try to polish the chamber a little with 0000 steel wool, but is there any merit to sending the gun back to Mossberg before trying anything?

    Also, if the chamber edge is a bit sharp is there a suggested way to specifically polish that edge so it doesn't scrape and slow shells as they enter?

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