Sounds like a cupseal leak.....

[kansas kaos]

First off I'm fairly new to 'mags' but I have a lot of experience with other markers (wgp,icd,etc).
I know that there really isn't a cupseal but that was the easiest way for me to describe the problem. Here's what happened...
I recently picked up a Classic Powerfeed Mag off ebay. When it arrived I aired it up and it didn't work..... yeah, go figure. It would load up air normally but as soon as you pulled the trigger air would just run out and the trigger would not return. So I started looking at parts of the valve I was familiar with (recently did an RT on-off upgrade on a classic valve). When I pulled the on-off assembly out I noticed only the small white o-ring at the bottom.... no larger one. So I found one in my parts box that would fit. (non-agd) I installed the o-ring, oiled the on-off assembly and reassembled the marker. The original problem was solved except for a small leak.... plus I got a nice benefit. The trigger pull is now very short, like putting the "firing point" timing of a Cocker way up front in the pull. I'm assuming the o-ring I installed in place of the missing one is probably just a little thicker and is acting like a shim? Anyway... as long as the suff is freshly oiled there is no leak, after a while you start to hear a faint leak that grows with time. I noticed if I LIGHTLY press on the trigger that the leak stops. I tried a little silicon grease on the larger bottom o-ring and it helps somewhat but doesn't fix the problem.
My question is am I on the right track messing with the on-off assembly area or am I hitting something closely associated with it by luck?

[Asym]

Is the leak coming from the bolt area(down the barel) or near the on/off? If your leaking without pulling the trigger its usually leaking down the barrel, when you pull the trigger and hold it back the on/off should be sealed and no air can leak down the barrel unless the on/off is leaking.

If its leaking down the barrel you need to find out if you have a level 7 or level 10 bolt. Level 7 has a slot on the power tube tip that you can use a nickel to remove, level 10 has a hex end that you need a wrench to remove. If its level 7 and leaking you might need a different sized spacer or a new powertube o-ring. If its level 10 you need a tighter carrier.

If its leak in the on/off look at getting a new oring kit and double check your pin length here . If thats right, look at picking up a rebuild kit .

[kansas kaos]

Well it seems the leak has decided to stop for now so I can't pinpoint it's origin for certain. I can say tho that I went and measured the pin. It's the standard length (.075).... I did notice that since I added the silicon grease that the small o-ring has slipped down into the larger o-ring (so it looks somewhat like a 'target'). Guess it's formed a better seal now...... i don't know. Um it has the slot therefore i guess making it lvl7, which is fine. It still has one star so if it gives me too many probs i'll just send it in for a rebuild. However I still wanna learn my way around these valves so I can maintain my marker or fix basic problems.
Anyway.... thx for your assistance thus far.

[Coralis]

I did notice that since I added the silicon grease that the small o-ring has slipped down into the larger o-ring (so it looks somewhat like a 'target'). Guess it's formed a better seal now.

Its supposed to do that