Barrel Leak

[Automag ReTro]

Need some help. I have a barrel leak that is extremely annoying. I am running an X-valve with a ULT trigger. The problem is this: usually the first shot of a string of shots, or really just the first shot after the gun has been sitting for a minute or two chuffs and send the rolling out the barrel, or stopping in the barrel. The next shot always fires. It never double chuffs unless I actually short stroke the trigger. I also noticed that if I pulled and held the trigger, it would slowly leak, then stop. After it stopped, it would chuff when trying to shoot, then fire again on the subsequent pull. I could RT the hell out of it. The first ball would chuff, then the subsequent massive stream of balls would be amazing and perfect. The gun chrono'd perfectly and in long streams of balls they would stay consistent and on top of one another.

I have read the forums, I have watched the videos, and I have spent a lot of time trying to figure this out but havent' gotten anywhere with it yet. In the TK videos where he troubleshoots common problems, he covers barrel leaks. However, he covers the "lawn sprinkler" effect which isn't what my gun is experiencing. Everytime I think I've got it fixed and shoot it succesfully without a barrel leak, the leak manages to come back just as I'm thinking it's fixed. Aftering playing all day today with this problem I came home and swapped out some o-rings for some fresh ones and for 100 rnds or so I thought it was fixed. Came inside to cycle some oil through my gun before I put it away and the leak came back.

I'm really frustrated with this and would like some input from you guys. Thanks a lot and I hope someone can shed some light on this.

[hill160881]

Take a shim out of the ULT.

Also it sounds like the L 10 bolt is leaking if you have a L 10. Take a shim out of it to or go down one carier size.

[Automag ReTro]

I'll have to get some more air and check that. I've tried everything between 2 and 7, but I haven't tried one shim yet.

[hill160881]

I'll have to get some more air and check that. I've tried everything between 2 and 7, but I haven't tried one shim yet.

What about the bolt? You need to put a stock RT on off in it to tune it right.

[Automag ReTro]

Are you asking if the Lvl 10 is tuned correctly? I believe it is. I don't have any barrel leaks while the trigger is released, just when the trigger is held and then the leak slowly stops. I'm pretty sure I have the smallest carrier in that won't leak. The next size down causes erratic velocity from too much bolt stick and the next size up leaks down the barrel when I air up. I can also basically walk the trigger with my finger in front of the bolt and it resets everytime so I'm pretty sure I've have it shimmed up correctly.

[hill160881]

The reason that it chufs when it sets for a while is possibly a small leak in the power tube. Thus it does not have enough pressure in the shot chamber for a full cycle. If it is not this then it is bolt stick. What is the entire setup? Spring color & length, carrier used, and # of shims in both the power tube and the ULT

If the ULT is not tuned right then it is hard to tell if the L 10 is tuned right. You should use the carier that caused inconsistent velocity and brake it in. Dont forget to drown it in oil first, 5 to 10 droops.

[Automag ReTro]

I've got 2 shims in the powertube and two shims in the ULT. Using the red bolt spring and the carrier with 1 dot and 1 ring. Chrono'd at 280fps.

[hill160881]

I've got 2 shims in the powertube and two shims in the ULT. Using the red bolt spring and the carrier with 1 dot and 1 ring. Chrono'd at 280fps.

Take out a shim in the power tube and turn up the markers velocity. If that solves the problem then you will need to cut down the spring a bit and re tune the bolt. I hate the L 10 bolt and use a gold bolt spring with the second smallest carrier. It will still chop but it wont leak, i use a rotor so i dont need the anti chop effect.
Check the ult orings because two shims should work fine. I would put the rt on off in to tune the L10 bolt if you have it.

[athomas]

You are experiencing bolt stick. The leak you are experiencing when holding the trigger is normal due to the small amount of residual pressure left in the chamber after a shot is fired. It isn't quite enough to force an instant seal.

To fix your bolt stick, you need to retune your setup. Its almost correct. You probably need the next larger carrier size. Remove all the shims from your powertube when tuning the level 10. They will induce false leaks if the bolt vent hole is close to the sealing surface of the oring. Use the largest carrier that does not leak. Always use the same white powertube carrier oring when changing carriers. It is the inner diameter of the oring that you are adjusting. I wouldn't worry about putting the shims back in. The amount of bolt movement on any jam is far enough to allow the bolt to vent air and reset without any shims.

To select the proper level 10 bolt spring, use one that allows the gun to operate at about 20fps past the velocity that the gun starts to cycle. If a bolt spring causes the gun to cycle at 270fps and you want to operate at 280fps, then you need to use a lighter/shorter bolt spring or cut down the one you have. If the gun starts to cycle at 240fps and you want to operate at 280 fps, then you might want to use a longer stiffer bolt spring.

[Automag ReTro]

Ok, gonna have to try to make an emergency run to the scuba shop after work sometime this week to fiddle will all of this again. I had Luke's sear mod done as well and I don't think this would cause any of the problems I'm having but I need to reverse this for the time being as well to get back to square one. I've tried removing the trigger rod per his instructions but I didn't get anywhere. Anyone have a good tip?

Also, while I was at the field and experiencing all this chuffing I decided to put in the RT on/off because I figured it was just the ULT out of tune. However, as soon as the new on/off was in everytime I fired the bolt on my finger it would stick forward and have to be reset manually. When I loaded it up with paint it wouldn't even fire. I'm pretty sure I just spelled out the bolt stick problem, but I'm also pretty sure if I go up to the next largest carrier it's going to leak. I'll just have to find some air and check all these shenanigans out again.

[Justus]

A couple weeks ago I had a similar problem: Sometimes I could hear a very faint leak down the barrel. After shooting, the leak would either get louder, get softer, or even stop altogether. This changed on every few shots. When I pulled and held the trigger, I could hear a faint slow leak that would stop after a second or two.

I completely fixed this issue by removing all the Level 10 shims from my powertube. I didn't have to adjust the carrier at all. And my RT on/off started acting much better afterward, too. So, I'd say start with the powertube and once that's fixed, see if you even still have a problem with the ULT.

[hill160881]

Athomas has better instructions, i did not explain it this well

[Automag ReTro]

Ok, so I used a little of the roommates air and tried a few things out. I took out all the shims in the powertube this morning and aired it up for a few shots. The barrel leak was gone but it was still chuffing. Just a few minutes ago I aired it up again and put 4 shims in the ULT. No leaks, no chuffs and the bolt reset after the finger jam test. Took it outside and fired a ball or two and there were no chuffs regardless of how long I waited between shots or if I held the trigger down for a second, then fired. The leak came back, but intermittenly. Sometimes I would hold the trigger down it would do the slowly leak then come to a stop, then on the next pull it wouldn't leak at all. I think as long as I don't have shootdown and it doesn't chuff the leak shouldn't be that big of a deal.

So hopefully it's fixed. I won't know for sure until this weekend when I get a full tank and can play with it again. But so far it's looking like it's good to go.

[Justus]

Add oil. That might stop the leak completely.

[athomas]

The seals should work without oil. Oil reduces friction. It does not seal. There should only be enough to moisten the oring. If adding oil fixes any problem, then the problem is only masked and will eventually return at the most inopportune moment. It is best to solve the problem than to mask it with a dose of oil.