A cone valve assembly including an upper valve member with a conical top portion and a stepped and spiraled top surface and a lower valve member including a central opening with a stepped and spiraled valve surface surrounding the central opening. The upper valve member is mounted in the lower valve member such that the lower valve member is rotatable and axially movable relative to the upper valve member. Rotation of the lower valve member allows for the adjustment of an arcuate slot opening that provides a conically shaped discharge stream of water from the cone valve nozzle assembly directly onto the rotating distributor to provide the desired arc of sprinkler coverage.