Rotate hammer spring screw counter clockwise to decrease spring tension. With the gun unloaded and pointed in a safe direction, fire the gun. The gun should not fire. Rotate hammer spring clockwise one full rotation and fire again. Repeat this step over again until the gun fires. Then rotate hammer screw one full rotation again and set the lock nut.
DON’S VALVES ONLY OPERATE AS AN ON-OFF SWITCH AND ARE NOT TUNED LIKE TRADITIONAL VALVES. USING TOO MUCH HAMMER SPRING WILL DAMAGE THE VALVE AND VOID WARRANTY.