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.