The classic valve regulates the air pressure at the top of the on-off pin down to working pressure which really reduces the return force on the top of the smaller ULT pin. If you have any restrictions or friction areas in your mechanical mechanism, it will affect the return because that friction becomes a larger percentage of the total force requirement. You can control your finger to reduce its effect on each shot, but you also need to make sure the actual physical sear mechanism is in perfect condition and not rubbing anywhere.
Originally Posted by ascent
The ULT won't accept a normal rt pro pin. They only accept the ULT pins due to the ULT having a different pin diameter.
Using a lot of shims in the ULT in the classic can help by reducing the distance that the pin needs to travel into the tip oring before the sear can release the bolt. This reduces some of the friction effect caused by the oring. However, it doesn't guarrantee results. Friction comes from many places. Chamber operating pressure also has an effect on the operation. The barrel you are using affects the operating pressure. Unfortuately, I think the less efficient your setup, the better a ULT will work in a classic valve. That is because the regulated air pressure is higher for an inefficient setup than for an efficient one.
Except for the Automag in front, its usually the man behind the equipment that counts.