ULT Tuning Help

[BlackOps]

Okay, I'm helping a friend of mine try to tune his RT ULE. We started by putting my regular RT on/off assembly in it and got it firing perfectly, and the level X all tuned in right. Everything fires and functions as it should with the regular ON/OFF in it.

So we put the ULT back in in order to begin setting it up as necessary. With 2 shims in it, it will shoot fine for about 10 rounds or so, then the on/off doesn't fully reset. The pressure still keeps the sear rod against the back of the trigger, when you pull it, it does fire, but the on/off does push out when you release the trigger.

(has been fully oiled up, and should be fine in that aspect, we have new o-rings should we need them, but I'm not convinced that is the problem at the moment)

So my question is: What needs to be done to get this thing running right?

I guess what I'm getting at is: adding more shims increase the chance of a runaway gun, what effects does removing shims have?

Any help would be greatly appreciated.

[bbotts77]

. The pressure still keeps the sear rod against the back of the trigger

This sounds like you might want to shorten the trigger rod. Most people will tell you that you want to have a gap the thickness of a credit card between the trigger and the sear rod when it is gassed up.

[athomas]

When it doesn't reset, can you push the bolt back and force a reset?

Try putting a couple more shims in. Increase shims, one at a time until the bolt sticks, or you get run away. Then remove the shim that caused it.

[BlackOps]

Yeah, forgot to mention. I had the grip off and tried to push the sear further to get it to reset with no luck.

Added 1 shim and it looks like we are good to go now. Thanks again guys!

Just trying to get used to figuring out when I need more or less shims for both Level X and the ULT.

[athomas]

Yeah, forgot to mention. I had the grip off and tried to push the sear further to get it to reset with no luck.

If the bolt sticks, you will not be able to push the sear forward. The bolt blocks it. You can force a reset by pushing the bolt back though. That allows the sear to rock forward into the reset position providing the stick isn't caused by the ULT.

Just trying to get used to figuring out when I need more or less shims for both Level X and the ULT.

In the level X, you shouldn't ever need any shims. Shims are only used to determine how far the bolt needs to move to vent air. Even without any shims, the bolt almost always moves far enough during a breach blockage. Basically, if the bolt fires at all or if it vents air or chuffs, then shims will not help it.

For the ULT, shims determine how far the sear has to move to release the bolt after the on-off closes. More shims, and you shorten the distance. Less shims and you increase the distance. With less shims, you risk pushing the pin farther up into the oring where friction can cause it to stick. The smaller diameter of the ULT pin reduces the return force on the top of the pin, so friction can be a nuisance some times. This usually goes away once the oring gets broken in. With more shims, you shorten the distance so that the ULT barely closes before the bolt is released. This reduces the distance the pin travels into the oring. The reduced friction makes the valve more responsive and therefore more reactive as well.

[BlackOps]

Thanks man, that was exactly what I was wanting to know. That way in the future if I have problems, I can more easily determine the cause and what the potential resolution is.

[TacOneFish]

Yeah, forgot to mention. I had the grip off and tried to push the sear further to get it to reset with no luck.

Added 1 shim and it looks like we are good to go now. Thanks again guys!

Just trying to get used to figuring out when I need more or less shims for both Level X and the ULT.

I have the same problem did you add the shim to the level 10 or the ULT? if so how many shims are you using in which ever one it is over all?

[BlackOps]

The shims were in the ULT.

When I first started looking at the gun, it was running away. It had 5 shims in it at the time. I took 3 out and started over at 2. Then it was firing a bit then not reseting all the way. Added one more for a total of 3 installed and it works like a champ. Hope that helps.