A sprinkler and side-loading nozzle insert assembly includes a sprinkler body provided with a flow passage, a bearing housing in a side wall of the sprinkler body, and a nozzle insert received in an access opening formed in the side wall of the sprinkler body substantially opposite the bearing housing. The nozzle insert includes an insert body having a bearing portion received in the bearing housing, a ball-valve portion connected to the bearing portion and provided with a nozzle bore having an inlet and an outlet orifice, and a lock/release portion connected to the ball-valve portion, the lock/release portion including plural, flexible spring arms extending away from the ball-valve portion. The nozzle insert is rotatable to plural operating positions by manipulation of the spring arms.