Problem with the air gun mechanism is that the gas that propels the BB and the gas that pushes the slide back come out the same valve, and into the nozzle. The nozzle is open at both the front and back. The front is for propelling the BB, the back acts as a cylinder with the piston head attached to the slide to blow back. There is a small floating valve and spring inside the nozzle that controls how much gas goes each way, you can file the back of the valve a bit to increase power but it will not decrease gas consumption.