68 Automag Major Leak

[ccrosland99]

I have a 68 automag that a friend gave me and whenever attach an air tank, there's a leak. But this is no ordinary leak. It drained a 12 ounce tank in a matter of seconds and it sounded like the roar of a dying lion. I have absolutely no clue where to start. Any help would be greatly appreciated, thanks!
I attached a few pictures. Hopefully that helps :)

http://m.imgur.com/APihce1,CKZaxZq,7O8UpL3,qDID63z,PPpEpJU,BmkuS0v

[BiNumber3]

Is the leak coming from the rear of the gun, the front, or the rail?

[ccrosland99]

It's coming out of the barrel. It seems like the valve is just staying in the on position.

[blackdeath1k]

Does it stop if you hold the trigger in?

[ccrosland99]

No, pressing the trigger doesn't really do anything.

[BiNumber3]

Does the mag fire?
Few things to look at:

Spring: Should be go past the bolt tip a good amount, if it's as long or shorter than the tip, you need a new spring
Bolt: Check how worn the back lip of the bolt is, should be pretty angled.
Sear: (The steel thing that swings in the rail) Check the sharp point that would catch the bolt, it it's rounded out, it'll need to be replaced (pretty rare in general)
Powertube: Unscrew the brass tip of the valve, check the o-ring

(If you can get some pics, it might help figure things out faster)

[Cyco-Dude]

...also double-check the sear rod length. it should not be touching the back of the trigger when the gun is aired up.

but really, if it has been sitting for a while, it might just be time to rebuild it. fortunately it's a simple process and doesn't take very long at all.

[blackdeath1k]

Just dawned on me. You said 12 oz. As in co2. If that mag has seen co2 all of its life ID venture a basic rebuild kit would make it run perfect.

When you said leak down the barrel I was thinking power tube Oring. But if pulling the trigger doesn't stop it that would add the on off Orings. And honestly back many moons ago when I used co2 because hpa was non EXISTANT. Them were the Orings that got froze and trashed.