xvalve first shot drops

[fhawkeye]

Level 10 / ULT

first shot seems to drop considerably, in a string the first shot will be 218fps followed by every shot being 275fps.

I have increased the carrier in the level 10 until it leaks, the leak is inconsistent between shots. Don't know what else to try or what else might be wrong.

[cockerpunk]

slow leak from out of the dump chamber probably. smaller level 10 carrier or slightly tighter oring, or possibly in the on/off.

[BigEvil]

No, because the dump chamber always has line pressure to it until you pull the trigger and the on/off goes to "off". If the gun sits, does the velocity drop again on the next first shot?

Check your reg pin orings and see if they are bad or have any crap in them. Velocity issues are always (I should never say always) in the regulator part of the valve.

[captian pinky]

small black oring in the ult or the top small one are my guess.

[Spider-TW]

Yeah, the only time I had a first shot drop off, the reg was sticky AND not keeping up with a tiny power tube leak. It was the night portion of a big game when I figured it out. Sneaking around on a 70 acre field around 10pm, I finally heard the power tube leaking.

More oil and better lvl 10 sealing required.

[cockerpunk]

No, because the dump chamber always has line pressure to it until you pull the trigger and the on/off goes to "off". If the gun sits, does the velocity drop again on the next first shot?

Check your reg pin orings and see if they are bad or have any crap in them. Velocity issues are always (I should never say always) in the regulator part of the valve.

ah yes, sorry, you are correct.

as big evil said, check the reg seals.

[fhawkeye]

yes, when the gun sits for maybe 30 seconds, the first shot drops down again.

[fhawkeye]

Could the leak possibly be a type of bolt stick? I added a 3rd shim, without a chrono on hand I can't speak for the velocity issues but may have solved the leaking issues?

[BigEvil]

Could the leak possibly be a type of bolt stick? I added a 3rd shim, without a chrono on hand I can't speak for the velocity issues but may have solved the leaking issues?

Could be, or you just loosened up the oring a bit.

[athomas]

Could the leak possibly be a type of bolt stick? I added a 3rd shim, without a chrono on hand I can't speak for the velocity issues but may have solved the leaking issues?

Remove all your shims and retune your level 10. The shims could be causing your to use a carrier size that is tighter than it needs to be. That could cause a tiny bit of sticking. The oring sticks more the longer it sits which is why you get sticking on the first shot but not on subsequent shots.

[fhawkeye]

Well now I am at a complete loss - I have took out the shims, now tried a couple different power tube o-rings, worked my way down and am now on the smallest carrier with no lines and dots, even tried replacing the power tube tip o-ring and still leaks down the barrel. Tried a couple different on/offs that seem to work great, leak stops when I hold the trigger down. For good measure replaced the plunger assembly behind the on/off. If I wasn't frustrated already...

[Cyco-Dude]

i think the issue here is with the ult, particularly the tiny black o-ring. i think replace that and you should be ok. you don't need to take the ult pin apart to remove or install it; it will stretch.

after that, re-tune the lvl 10 to use the largest carrier that doesn't leak, as you're likely using one that is too tight now.

[fhawkeye]

i think the issue here is with the ult, particularly the tiny black o-ring. i think replace that and you should be ok. you don't need to take the ult pin apart to remove or install it; it will stretch.

Switched it out with the on/off that came with the mag (non ULT) with no change

[nak81783]

Tried a couple different on/offs that seem to work great, leak stops when I hold the trigger down.

Is the tip of the sear worn? How is the condition of the bolt where it engages the sear? Do you have another bolt to try? I had one way back in the early days of the Level 10 that had an improperly pressed stem. It would leak at the pressfit joint no matter what.

Going back to your first post, it isn't clear if the first shot drop is due to a leak or stick. With all the talk of a leak, are you now more confident it was from a leak rather than stick?

Oh yeah, one more thing, is your rail bushing in place?

[athomas]

Check to see if your rail bushing is in place.

When it is leaking, can you stop the leak or slow it a bit by pushing back on the tip of the bolt.

Also, if you use a carrier size that is too tight, the leak might not go away, because the tight fit of the bolt stem pushes the oring back rather than allowing the bolt stem to fully move the vent hole past the oring.

Check the sear for wear. A worn sear will allow the bolt to sit too far forward.

Check your bolt stem to see if it hasn't come loose. They are press fit, but sometimes come apart. This is rare but has come up a few times recently.

Are you sure the leak is the powertube and not a leak in the chamber where the powertube screws onto the valve body, or a leak between the front and back half of the valve.