Abstract: An impact type rotary sprinkler is disclosed including a rotatable body and nozzle, an impact arm which oscillates responsive to the kinetic energy of the fluid discharge stream and a primary spring which stores the rotational energy of the oscillating arm rotating to impact against the housing and impart an increment of rotation thereto. The sprinkler is adapted for uniform water distribution over a range of discharge stream kinetic energies in excess of design limits by the provision of a secondary spring which is operable when the impact arm rotates in excess of a predetermined arc due to excessive rotational force being applied to the impact arm. The secondary spring assists the primary spring in urging the impact arm in the opposite direction.