Leaking down the barrel

[wolftune]

First, I know this question has been asked many times on this forum, and I've read as many posts as possible, but I've read conflicting answers. I've also (gasp!) looked on other forums and found the same conflicting advice, so I need a definitive answer, if possible.

I recently picked up an old classic automag for cheap and want to restore it. I believe it's all stock parts, level 7. I swapped it's stock grip/trigger frame with the benchmarke trigger frame from my minimag (my primary marker now). I was chopping a bit with the benchy and don't want to use an electric hopper, so I'm downgrading. Actually, I didn't like the benchmark much anyways and prefer the slower, crisper rate of fire.

In any case, the automag was firing fine when I first brought it home. When I switched the grip frames, it started leaking down the barrel. It leaks until I fire. If I hold the trigger, it stops leaking. As far as I can tell from the posts I've read, these are my potential problems:

- trigger sear adjustment (unlikely)
- pt o-ring (i replaced it with another, slightly newer one and it made no difference)
- power tube spacer (this one has a spring spacer. I suppose this could be it but why would it have changed by me switching out grip frames?)
- on/off valve (I changed the two teflon o-rings and it made no difference)
- bushing (as far as I can tell, my bushings are intact)

Soooo....can anyone tell me definitively?

I read some posts that said that if the leak stops with the trigger pull, it's the spacers. I read other posts that said that means a problem with the on/off. Any advice is most appreciated.

Oh, and I did oil it but I'll giver her another drink to be sure.

Thanks in advance. I'm an automag addict now...

[secretweaponevan]

<long>Automags are really simple.

1st and most important thing to remember always:

If it leaks down the barrel with the trigger at rest, you have a leaky powertube o-ring.
If it leaks down the barrel with the trigger pulled, you have a leaky on/off (top) o-ring.

When you pull the trigger, the on/off goes to "off" shutting off the gas supply to the bolt right before the sear releases the bolt which flies forward, expels the gas in the dump chamber and is then reset by the bolt spring. Watch the TK Automag videos on youtube: http://www.youtube.com/watch?v=vehPc7vuK20
You'll be an expert in less than 2 hours.</long>

<short>You need a spacer kit.</short>

[jrod]

Pick up a spacer kit. That should fix your problem.

[Watcher]

Yup, spacer kit will solve the issue.

You want to use the biggest spacer possible without leaking down the barrel.


As far as switching grip frames causing a leak, make sure that the trigger rod isn't too long for the stock frame.

It could be depressed slightly causing the sear not to sit right. This is not the cause of the leak, but it can't have helped.

The trigger rod should be a mm from the back of the trigger when you pull it with the safety on.

[wolftune]

Yup, spacer kit will solve the issue.

You want to use the biggest spacer possible without leaking down the barrel.


As far as switching grip frames causing a leak, make sure that the trigger rod isn't too long for the stock frame.

It could be depressed slightly causing the sear not to sit right. This is not the cause of the leak, but it can't have helped.

The trigger rod should be a mm from the back of the trigger when you pull it with the safety on.


Thanks, everyone, I'm ordering a power tube spacer kit.

Does that 1 mm rule apply to the benchmark trigger as well? Right now, it's more like 5 mm.

[Watcher]

Yes, it applys to whatever frame you use.

And when you say 5mm, is the marker gassed up? That is an important step in setting the trigger rod.

[wolftune]

Finally got my spacer kit. I replaced the pt oring with a new one and tried all of the sizes. None of the sizes stop the leak. It still is leaking when I air up the marker with the trigger at rest. The leak even 'sounds' the same with each spacer.

Strangely, different spacers have an effect on when I pull the trigger. With some sizes, it leaks both with the trigger at rest and also when I pull and hold the trigger. With others it stops the leak when I pull the trigger. What could that be? I've cleaned the on/off and replaced the two teflon o rings, seemingly to no effect on its own.

Part of me thinks this whole thing has to do with switching to the benchmark frame, because this valve was not leaking at all before I switched it out. Is that possible? There's about a 2 mm gap between the trigger and the sear pin when it's gassed up.

Oh, and the leaking down the barrel really sounds like it's leaking from the trigger, but I suppose that's probably where it would 'sound' like it's leaking.

Any ideas? Much appreciated in advance.

[Wanta B Sniper]

Put the valve, only the valve, into your Minimag and try adjusting the spacers then if it is still leaking, let us know if that works.

[DamianTC]

did you replace the power tube o-ring?

[Wanta B Sniper]

Yes he did, no change.

[secretweaponevan]

If it leaks down the barrel with the trigger pulled, you have a leak in your on/off.

I suspect you need to change out a few o-rings in your on/off since the leak sounds like it is coming from the trigger area.

Until your leak stops when the trigger is held, your on/off has leaks. Fix that before you move forward to the powertube.

[wolftune]

Okay, I have a kit on order to replace all the o-rings.

I switched the valves (with my minimag valve) and the automag still leaked with the stock frame. However, it was not leaking with the trigger pulled with the stock frame. I then threw my minimag valve in with the benchmark frame and it was perfectly fine. Still, I wonder why the on/off for the automag doesn't seem to be ieaking with the stock frame but is with the benchy.

I'll try the o-ring change and hope it fixes everything. Thanks.

[Wanta B Sniper]

Okay, with the stock frame the 68 Automag valve leaks down the barrel, correct? Problem is power tube spacer.

With the Benchy the problem is... It's not an AGD part :rolleyes: Uh, likely some kind of alignment problem. Shouldn't be though because the valve only touches the rail and body. Leaking from the grip frame is likely a bad bottom urethane o-ring on your on/off. Until your rebuild kit gets here try switching that one with the one on your power tube tip if it looks to be in better condition.

[wolftune]

[QUOTE Leaking from the grip frame is likely a bad bottom urethane o-ring on your on/off. Until your rebuild kit gets here try switching that one with the one on your power tube tip if it looks to be in better condition.[/QUOTE]

Funny you should say that, that's exactly what I tried today. It slowed the leak a lot but there was still some air coming down the barrel. So I found some on/off teflon orings lying around and swapped them out (seeing which were the tightest fit on the on/off 'rod' (not sure what it's called). Worked perfectly. Thing is shooting darts now. I switched these out before, but I never bothered to check how tight the fit was, so the "new" ones didn't work well either.

So the powertube spacer was never an issue really. Thing is, I swear the sometimes the trigger would not leak when I was holding it down, so I just assumed it was the powertube (after learning that leaking down the barrel is usually that). That's what threw me off.

Thanks a lot guys, big help. Now I've got an Automag and a Minimag working great. Some friend of mine will be lucky enough to borrow one...

Much thanks.