Reply To: Mac 1 USFT ???
I have never shot or even seen a USFT in person, so I am answering based on experience with other lower fill pressure guns. As an example, the Benjamin Discovery is a 2000psi gun, yet it can shoot .177 and .22 cal pellets just as fast as a gun that is filled to 3000psi. But, if the disco was safe to fill to 3000psi, it wouldn’t fire or atleast not very fast anyway in stock form, as the valve would probably lock due to the much higher fill pressure. It takes a certain amount of hammer inertia to over come the valve poppet based on how much pressure is in the storage side of the tube or bottle. This sort of illustrates the basic principle that fill pressure vs hammer weight combined with hammer spring tension is a balancing act of sorts.
Valve porting and a whole bunch of other variables can contribute to the success level of tuning and or designing a gun for certain pressures, speeds, etc. The increased shot count I assume comes from some sort of anti hammer bounce design coupled with a very efficient gun to start with.
Just my 2 cents worth, but I could be totally wrong as i have no clue how the usft was built.