ULE Trigger Tuning

[Jack & Coke]

Originally posted by BlackVCG
If you can't visualize what is happening with the trigger geometry, fire and release points, etc. you are better of leaving things alone.

It's like messing with the engine on your car. If you pop the hood and start adjusting things, taking them apart and putting them back together and don't know the mechanics of it all, it's going to run like crap once it's back together.

Excellent!!!

[openboater]

I just inspected the bolt and found NO WEAR. Probably 10-14 thousand shots.

I know what wear looks like cause I once had a hyperframe that eat bolts.

Remember, leave a gap between rod and trigger before firing, and a gap between trigger stop and grip frame after firing. Start with more gap, and shorten it up as you get more experience with it.

As far as doing this with a RT / Retro, it should work, but because of the increased reactivity, I've left mine stock. The forces are such that I don't notice the increased travel.

[athomas]

Re: got it

Originally posted by QUINCYMASSGUY

OK, an inquiring mind wants to know.... what are the technical terms for the physics principles that result in the ULE on/off allowing the pull weight to be dropped by 66% and the physics principle that explains why the original pull was 3X more?

Is the reduction entirely the result of the smaller on/off pin top?

When the front chamber is fully charged the only pressure on the on/off pin is the pressure exerted on the small section of the on/off pin. This is a mathematical calculation.

(Top area of the pin) minus (bottom area of the pin not included in the stem) equals the pressure area that the air will push on. The resultant area is the small section area of the pin. Since the force is equal to the psi multiplied by the area we get a force in lbs.

The old pin had a larger pin diameter at the bottom. Therefore the force exerted was also larger.

The recharge of the valve is another part of the pin. The recharge force is initially excerted on the top of the pin. The larger area of top of the pin combined with the higher input pressure of the retro valve is the reason we have a reactive trigger. By reducing the area of the top of the pin, we reduce the initial reactive recharge force.