ULT pressure requirements

[magfan]

Just a couple of quick questions.

What is the least amount of pressure required for reliable ULT performance?

What is the optimum pressure?

Thanks!

[athomas]

What type of performance are you looking for? The ULT works well at 800psi in most RT setups, but if you want reactivity, you need a higher input pressure.

It somewhat depends on your setup. The type of bolt and barrel have a lot to do with how the ULT works because it changes the amount of residual pressure left in the chamber after a shot. This affects the differential force between the top and bottom of the ULT top section. The difference is essentially the available force to move the sear assembly.

The amount of force to move the sear assembly is constant. Therefore, any change to the system that causes the residual chamber pressure after a shot to increase will require an increase in the input pressure to maintain the same operational performance.

I'm guessing that the minimum ULT pressure difference requirement just to push the sear reliably is about 400psi. The residual pressure for a middle spring configuration is about 150psi. You need approximately 200psi of difference between input and output for a good recharge rate. Therefore, any input pressure over 750 psi should work as a minimum value.