The screw under the regulator is the adjustment screw for the HPR. There is another adjustment screw right under the barrel, which is the LPR. Screw both in all the way. (clockwise) Turn air on. Turn the HPR (regulator adjustment screw) counter clockwise untill the gauge reads 250 psi. Then turn the LPR's adjustment screw (under barrel) untill you reach your desired FPS.