Leak Diagnosis/Schooling a Newb

[BrettEAS]

I've duplicated this post with MCB to cast a wide net, trying to find the mag experts.

Hi all,

I decided to disassemble my mag tonight after an issue I had while playing. While taking a shot it would leak slightly, then stop until I pulled it again. Before I continue, here's the setup.

ULE mechanical mag with LVL 10 and ULT. Gold spring, 2 shims in the LVL 10, 5 in the ULT. Bought new from AGD, 1st owner, approx. 1.5 cases through it.
Running on a crossfire 68/45 at approx. 850 psi.

To solve the problem, I dumped in more lube (Autolube) into the fitting on the reg. Gassed it up, no joy. It sounds somewhat like POPHSSSsss...POPHSSSsss...., with each hiss happening after I held down the trigger and only once before it stopped. It is not the "lawn sprinkler" effect where it happens continuously with the trigger held down.

So, I pulled out the on/off, saw no visible damage/debris in the orings, added more lube, and tried again. POPHSSSsss...POPHSSSsss...

At this time I replaced the small top urethane o-ring. No change. I changed the small black oring that rides the stem of the on/off. No change to the leak, but then air starts coming out the barrel. I took out the shims and changed the powertube oring, then downgraded to a 1.5 carrier which stopped the leaking down the barrel. I crossed my fingers that this would magically help the on/off problem , then pulled the trigger. POPHSSSsss...POPHSSsss...

This is beyond my mag knowledge at this point. When I disassembled the mag, I took all the components apart for cleaning since it had been awhile.

So, in addition to just what is causing my leak, I pose additional questions:

- The sear retaining screw on the ULE rail, how tight is it supposed to be screwed in? On initial reassembly, it would go damn near auto on me as I gassed it up. I tightened it up, then backed off enough to where the trigger rod would make contact with the trigger.

- How many shims do most people run in their ULTs? I had 5, and before the current problems I could get it to sometimes RT, sometimes not. Is my mag truly capable or RTing reliably with 850psi?

[Coralis]

did you mess with the regulator section of the gun if so try turning up the velocity some.

[BrettEAS]

Actually no, that part I left alone. seems to still be shooting ~300 fps.

[athomas]

Go back to 3 or 4 shims in your ULT first. That way you can tune your level 10. Ignoring the leak after a shot, use the largest carrier that does not leak while the gun is gassed up and ready to shoot. Make sure there are no shims in your powertube. Once you find the proper level 10 setup that allows you to fire without leaking, then add shims to the ULT.

Make sure the bushing is in place at the back of the rail.

[Ando]

Sounds like a shim leak brother. Pull all your ULT shims out and see if the leak is still lingering.

6 shims is "max" for a ULT. 99% of the time you start getting into body clearance issues with anything over 6. The amount of shims too keep in is up to you. Keep adding till you get the trigger feel you're wanting or it starts leaking then go back one.

- The sear retaining screw on the ULE rail, how tight is it supposed to be screwed in? On initial reassembly, it would go damn near auto on me as I gassed it up. I tightened it up, then backed off enough to where the trigger rod would make contact with the trigger.

Sound like you're talking about 2 separate things. Your sear axle should be snuged down. Your trigger rod shouldn't be touching the trigger. You need a small gap between the sear arm and trigger. That's probably what's causing your full auto problem.


EDIT:
When you do pull the trigger. Does the "POPHSSSsss" sound like it's slow to recharge?

[BrettEAS]

Ando,

I wasn't being totally clear in my writing. The powertube leak was corrected, sorry for making you guys type that info out again, I see it all the time when I browse the threads.

I was in fact referring to the sear axle, when I tightened things down after the mag went auto after I gassed it up, I went a little too hard and the trigger rod would barely clear the frame (thus the trigger could not make contact). I loosened it to the point where it would move freely when I held the degassed gun downward.

I have since taken one shim out of the ULT, and no longer experience full auto.

As far as what the POPHSSsss sounds like, I'm in the middle of filming it to try and put on youtube. Until then, it sounds like there's some residual air that leaks when I hold the trigger, but it lasts for a second and then stops. It's pretty weak, the "lawn sprinkler" effect in Tom Kaye's video was fairly loud.

I'm off to refill my air tanks and try to record this in video, since that should explain things better than I can.

[athomas]

.... it sounds like there's some residual air that leaks when I hold the trigger, but it lasts for a second and then stops.

That is standard level 10 leak down when holding the trigger. The low residual pressure can't exert enough force on the oring to cause it to seal against the bolt stem. It is normal.

[BrettEAS]

I gotta say I had a laugh that after all this...it's normal! Thanks for the help.

[BrettEAS]

Here's the footage I recorded:

http://www.youtube.com/watch?v=t7wojPFP-JE

I returned everything to the way it was when I started, so here it all is:

LVL 10: 2 shims, gold spring, #2 Carrier. Works well, powertube leak did not return, bounces off a squeegee in the breech. Less than two shims and it doesn't reset well.

ULT: New orings, 5 shims. Doesn't quite RT for more than a few shots, sometimes feels like bolt stick when I try to get it to RT for long. Shortstroking perhaps?

And lots of oil.

This is what I was talking about, a lot more clear than I could explain.

[Ando]

That's def a on/off issue. Try a stock on/off and/or replace all the orings. That should hopefully fix it.

[BrettEAS]

That's def a on/off issue. Try a stock on/off and/or replace all the orings. That should hopefully fix it.

I replaced the small urethane oring at the top of the on/off (that the pin slides through), as well as the tiny black oring that sits at the pin's base. The pin doesn't appear bent/nicked/deformed. I took out one shim (total 4), but I'll have to just take them all out and see what happens.

When I reassemble the on/off halves, they still swivel freely, which I assume is what's supposed to happen since it doesn't look threaded in a way that it would screw tightly together. Does this sound correct, in addition to reducing more shims?

[athomas]

LVL 10: 2 shims, gold spring, #2 Carrier. Works well, powertube leak did not return, bounces off a squeegee in the breech. Less than two shims and it doesn't reset well.

Thats bolt stick. If you need shims and lots of oil to make it reset, then the carrier is too tight.

If it fires or vents at all, then shims won't help the problem. Oil will mask it, but it will return. A ULT leak could cause air flow into the front chamber that could be offset by shims. The shims could allow the excess air to flow out of the chamber and allow the bolt to reset if the ULT leak was small enough.

The on-off halves should tighten up when you screw them together. Make sure you aren't using level 10 shims in the ULT by mistake. The level 10 shims are twice as thick as the ULT shims, so each level 10 shim represents 2 ULT shims.

[BrettEAS]

Okay, now we're getting somewhere. All my shims ended up in the same plastic bag...

I also didn't see ULT shims available at AGD's store, only the LVL Ten variety. Are they sold separately from the whole kit?

[Ando]

Talk with Tuna on the ULT shims. You "can" use lvl 10 shims in the ULT but just remember they're twice as thick as athomas noted, so a "max" of 3 lvl 10's can be installed. You'll be fine if you have at least 1 ULT shim for tuning purposes. Get a set of calipers, you can sort the bag out or just eyeball the shims (you can tell the difference). Your on/off issue might be you using all lvl 10 shims.

The stock on-off halves should tighten up when you screw them together.

Fixed

[BrettEAS]

Here we go:

I took out all shims from the LVL 10 and ULT. I visually inspected each freakin' one, and separated them this time.

Went up one carrier size on the level 10, it leaked, I went back to #2 where it was originally. No leak. No shims.

I replaced the inner two orings, and outer two orings of the on/off. All orings are now new.

0 shims in ULT: Gasses up, no click from sear/trigger, will not fire.

1 shim: Will not fire

2 shims: Will not fire

3 shims: Leaking upon gassing up while pressure builds, then stops. Will fire, but leaks and slowly pressure builds to re-cock itself.

4 shims: Recocks fine, original problem of a leak after pulling the trigger resurfaces.


So it would appear I'm back at square one.


How's that RT on/off?