Common causes of an unreliable trigger?

[Trbo323]

Figured I'd pick the brain of the swarm here before I go willy nilly tinkering

X valve, ule on/off
Can't remember the tank input pressure off the top of my head but I think it's around 850

Marker fires, makes velocity but the pin seems to be sticky. Sometimes it resets fine, sometimes it doesn't. Usually waiting and pulling the trigger a few more times (it won't shoot) gets the pin to click back and reset.

My gut is saying too many shims in the ule?

Does pin length matter on a ule or no because of the shims?

Bolt spring? I have gold spring in right now if it matters

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[superman]

Make sure it is oiled.
more shims equates to a shorter pin as if it was a rt on/off.

pretty much the reason I hate the ult.

[nak81783]

Isolate variables if you can.

When it sticks, does pushing the bolt back with a swab reset it? If yes, focus on bolt stick causes - bolt spring, carrier size, stem o-ring.

If no, then focus on the ULT. I’ll be my typical broken record self. First, I don’t like the ULT; replace it with an RT on/off. However, that alone may not resolve the issue. Second, I don’t like AGD o-rings. Sure, they last forever, but they also seem too tight at the beginning and take forever to break in. Use millable gum urethane D90 from theoringstore.com. They still last for tens of thousands of shots, but they work when you first put them in. Depending on age of the valve, you also may need to file down the RT on/off pin (non-head side) to get an OAL of .740-.745”. Newer valves seem to need a shorter pin. Go slow, and test often.

[Trbo323]

I also have an RT but I'd like to get the ule running

Plenty of oil in it although I'll put some directly on the ule and see if anything changes.



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[tunaman5]

when it sticks, try tightening the field strip screw and see if it clicks