A Plea for Help: Multiple Leaks in my old Classic Mag

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  • jay8533
    Newbie
    • Dec 2025
    • 9

    #1

    A Plea for Help: Multiple Leaks in my old Classic Mag

    Howdy folks.

    So, one of my kids found my gear bag in storage. Two months later, as these things go, he and his mother love paintball and have new modern markers while I'm trying my best to get my Classic valve mag up and running again. I gassed it up, leaks everywhere, immediately ordered a rebuild kit. Replaced (almost) all of the o-rings, and am left with two issues that I can't figure out - hoping someone can give me some guidance.

    There are no leaks with the regulator nut in the position shown below. A slight turn in leads to leak #1 (on/off) and a little further leads to #2 (reg/valve body seam). The bolt is not cocking (term?) no matter how far I turn it.
    ​

    1. Leak from on/off.
    I'm getting air from above the trigger, which I see typically attributed to the on/off. When I pull the trigger, the leak stops. I've replaced all of the o-rings in the on/off save one that appears to be in decent shape...and I have no idea how I would stretch the new o-ring into place if it needs replacing (on/off bottom o-ring). One of three things happens when I put the assembly back in - it either sits very loosely and falls out, or it rebounds back out when I push it down as if the top o-rings are compressing and then springing. Occasionally I CAN get it to seat in there, but once I gas it up the whole assembly is clearly coming loose again. I'm using the o-rings supplied with the rebuild kit from AGD.
    ​​

    2. Leak from reg/valve body seam.
    I replaced both the reg seat and the reg body o-ring, but it is leaking a fair bit. The two pieces seem to screw together further than I remember, such that the "Automag" etching on the outside isn't lined up. I feel like I saw a post here with folks saying they have had issues with the body o-ring in recent kits, but now I can't find that post.
    ​​

    Unfortunately I don't have a collection of known working parts or other marker builds to test things on. I'm hoping to figure out what I'm doing wrong here before looking at the upgrade options that either were not available or I wasn't aware of back when I played regularly. If there is anything I can check or other pictures I can provide, I'm happy to do so. Thank you for any suggestions!
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  • Shrimp266
    MCB Member
    • Jul 2020
    • 56
    • Fox Paintball

    #2
    For leak 2. Try flipping the reg seat. And oil both the seat and body o ring.

    For leak 1.lThe only thing i can think of is the orings in the bottom of the on/off are wrong. The on/off should be flush with the valve body, not the cut out where it sits.

    Comment

    • jdgreen76
      Bunker Buster
      • Sep 2023
      • 289
      • NY

      #3
      Leak 2 - I just bought o'rings separately to have around for when the kit o'rings don't seal.
      Feedback

      Comment


      • jay8533
        jay8533 commented
        Editing a comment
        Are you using something other than the ones AGD sells?

      • jdgreen76
        jdgreen76 commented
        Editing a comment
        I just grabbed some from captain o'ring I think it was.
    • Drcemento
      Tiger Stripe Enthusiast
      • Aug 2021
      • 741
      • NorCal

      #4
      Replace everything regardless of shape. Mags love oil, so make sure you have the proper lube- from agd, which is just outlast, and lube everything as you put it back together. Flip the reg seat lube it and try again.

      Comment

      • jay8533
        Newbie
        • Dec 2025
        • 9

        #5
        Thanks for the tips, folks.

        I replaced the one remaining old o-ring on the on/off, but it didn't change anything. Took it apart, wiped it all down, and re-lubed for the fifth or sixth time...and the leak from the on/off seemed to stop! Huzzah.

        Moved on to the leak #2. I had tried both sides of the new reg seat a couple times, so for the hell of it, I put the old one in. New lube and...still leaking...but maybe a bit less. Figured I'd try flipping that one and see. Removed the valve and the on/off popped out as if it were under a little bit of pressure. I didn't expect this as the gun hadn't been getting enough air to cycle, so I couldn't even shoot-down while removing the tank. I put the on/off back in...and now I seem to have the "sprinkler" problem in addition to air still leaking around the reg/valve seam. In the old AGD maintenance video it mentions this being a problem with the small o-ring on the on/off, so I tried each of the other two I have with no luck.

        Soooo...yeah :P

        Comment

        • Drcemento
          Tiger Stripe Enthusiast
          • Aug 2021
          • 741
          • NorCal

          #6
          did you rebuild the reg in the back? dissasemble and grease with dow 33 correctly? could it be a pressure thing? whats your tanks output pressure?

          Comment

          • jay8533
            Newbie
            • Dec 2025
            • 9

            #7
            Originally posted by Drcemento
            did you rebuild the reg in the back? dissasemble and grease with dow 33 correctly? could it be a pressure thing? whats your tanks output pressure?
            I initially rebuilt the reg, but used the same oil I used everywhere else - there seems to be a lot of different takes on this. But, I just went back and did it again using a dow 33 derivative. The sprinkler problem seems to have stopped, though I'm still a bit suspicious of the on/off. I'm wondering about the pressure, too, now that you mention it; I've only been able to test it on two generic regs that came on cheap steel tanks. Supposedly they output at 800, but I don't have a way to confirm. Waiting on a new tank to come in, which I had to get anyway, and will see if there are different results with that.

            Comment

            • Kit352
              Bunker Buster
              • Feb 2025
              • 410
              • Central mass

              #8
              Do you know what fps your shooting? You might be shooting hot and that reg seat will always leak potentially. I've found a lot of reg leaks happen when the gun is shooting hot.

              Those cheap steelies are pretty bullet proof. If anything they would be under pressuring but I've tested dozens and they are all around 800psi.

              Comment


              • jay8533
                jay8533 commented
                Editing a comment
                Right now it wont even cycle to fire as I start getting leaks as I turn in the reg nut, so I'm not at the point of having a measurable velocity. On the tank front, I've tried two generic Warrior steelies, but have a Ninja reg and a bottle on the way to test.
            • Meglomachinist
              MCB Member
              • Mar 2025
              • 258
              • Azle Texas

              #9
              I had one do something kind of like that but it wasnt a factory on/off so I canned that one and dropped in a factory unit. Have to make sure you seat the small ring that goes inside the valve body on the shaft. Sometimes if you drop it in then push the shaft in it won't cycle. Then crank the reg all the way up then back. I had that one picky one vent till it got to a high enough pressure then I stopped after cranking to the top and backing off. If that doesn't help I'd say it's the wave spring pack or the reg seat. And as stated before oil everything.

              Comment


              • jay8533
                jay8533 commented
                Editing a comment
                I seem to have gotten it working, the only thing not quite right is what you are talking about here; I get venting out the back when I first engage the air system but it seems to stop after a second - I'm guessing the small o-ring isn't quite seating correctly until there is pressure.
            • Meglomachinist
              MCB Member
              • Mar 2025
              • 258
              • Azle Texas

              #10
              Did you open up the reg piston body and flip the little rubber disc? Can be kind of a pia since that screw can be fun to get out without mauling up the brass body. Check that as well.

              Comment

              • jay8533
                Newbie
                • Dec 2025
                • 9

                #11
                Ok!

                So, after following the advice given by many here and replacing half of the o-rings a second time (and the reg seat three times) and oiling (and re-oiling) five or six times...I seem to have it working! I was still dealing with a leak from where the reg and valve body meet - what made the difference was backing off how much I had them tightened. I guess the reg body o-ring can be compressed if you over-tighten here? I've seen others comment on this both ways, but in my case, having the "AUTOMAG" logo lined up, even though it felt slightly loose, seemed to make the difference. Aside from that, it seems like the trick is to just have a large enough collection of o-rings?

                Using it again is wild. Last time I had it out to a field was in 2010 and I caught grief for using it. Took it out this past weekend and I had three or four people ask if they could fire it a bit at the chrono station or on the walk out to the field.

                Thanks for the help. Going to use it a couple more times before buying the upgrades that were not available (or I couldn't afford) as a kid.

                Comment

                • Meglomachinist
                  MCB Member
                  • Mar 2025
                  • 258
                  • Azle Texas

                  #12
                  Awesome that's great news man....just saying once you get bit by the mag bug....you are forever changed....welcome to the band of brothers.

                  Comment

                  • FredMnkyDad10
                    MCB Member
                    • Apr 2021
                    • 2259
                    • https://www.mcarterbrown.com/forum/buy-sell-trade/feedback/129612-fredmnkydad10

                    #13
                    Originally posted by jay8533
                    Ok!

                    Thanks for the help. Going to use it a couple more times before buying the upgrades that were not available (or I couldn't afford) as a kid.
                    This is how mags breed, worse than gremlins. Next you will saying oh I only need a rail or valve and I got another mag.

                    Welcome to the addiction.
                    FredMnkyDad10 Feedback

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