Leaking out barrel

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  • Railgun
    Hit me, I'm a target
    • Jan 2007
    • 93
    #1

    Leaking out barrel

    I've got a PTP body set up with a Minimag valve. I just bought it and it's shooting OK but if I pull slowly or just a little it leaks down the barrel just before firing. The power tube is set up with a purple Oring spacer and the Oring is grabbing the end of the bolt just fine.

    I re-watched the AGD video that answers so many questions and there's nothing in it that addresses this.

    I have a 32* rebuild kit and replaced the teflon washer in the on-off that seemed to be a bit loose on the on-off pin. At first it seemed to help but when I tried it today it was leaking just as bad.

    Thoughts on this leaking issue?
    Tags: None
    • athomas
      Of course it works-its AGD
      • Jan 2002
      • 8039
      #2
      When you slightly pull the trigger, you are allowing a slight bit of bolt movement which allows the bolt to move forward from the powertube oring. To prevent this leakage, you need to go to the next shorter powertube spacer. It will keep the oring engaged with the end of the bolt stem until the bolt is actually released, thus preventing any prefiring air leakage.
      Except for the Automag in front, its usually the man behind the equipment that counts.

        Comment

        • Railgun
          Hit me, I'm a target
          • Jan 2007
          • 93
          #3
          Originally posted by athomas
          When you slightly pull the trigger, you are allowing a slight bit of bolt movement which allows the bolt to move forward from the powertube oring. To prevent this leakage, you need to go to the next shorter powertube spacer. It will keep the oring engaged with the end of the bolt stem until the bolt is actually released, thus preventing any prefiring air leakage.

          Gotcha! And thanks. As it came I noticed that the space between the bolt face and bumper washer is only about 1/32 inch or perhaps a touch less. If I push on that then it seats the bolt into the Oring. So I need to swap spacers.

          Can anyone suggest what the space should be when the bolt is sitting ON but not IN the Oring? I'll shoot for closer to 1/16 for now.

          And one other silly question. If I install a shorter spacer what holds the Oring further ahead and against the spacer? AFAIK there's no spring or such behind the Oring.
          Last edited by Railgun; 11-21-2007, 03:40 PM.

            Comment

            • athomas
              Of course it works-its AGD
              • Jan 2002
              • 8039
              #4
              Originally posted by Railgun
              And one other silly question. If I install a shorter spacer what holds the Oring further ahead and against the spacer? AFAIK there's no spring or such behind the Oring.
              The air pressure in the chamber keeps the oring pushed forward against the back of the bolt stem to provide a good seal. The spacer keeps it back far enough to allow the bolt to reset properly. If the spacer is too long, it keeps the oring from sealing against the back of the bolt stem. If the spacer is too short, the bolt will not reset properly and you will experience bolt stick.
              Except for the Automag in front, its usually the man behind the equipment that counts.

                Comment

                • Railgun
                  Hit me, I'm a target
                  • Jan 2007
                  • 93
                  #5
                  Thanks again. The position of this Oring wasn't explained well in the Automag Owner's video since it showed a spring only so it wasn't adjustable.

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