Stubbers, I use the Pyramyd PCP Fill Caculator (always wondered how accurate it was??). I use 66 cubic foot SCBA tanks filled to 4500 PSI. MY FX has a 300cc tank. I fill it to 3300 PSI and refill it at 150 BAR. I get 48 shots (six mags) before refilling. The Pyramyd Caculator shows 19...