A sprinkler and side-loading nozzle insert assembly includes a sprinkler body provided with a flow passage and a nozzle insert seated in a complementary recess in said sprinkler body. The nozzle insert is rotatable to plural operating positions and it includes an elongated, substantially cylindrical insert body having an insert axis about which the nozzle insert rotates. A nozzle bore extends through the insert body on an axis transverse to the insert axis and alignable with the flow passage in one of the plural operating positions. A forward end face is provided with a turning knob and plural index tabs extending radially from the insert body at circumferentially-spaced locations proximate the forward end face. The index tabs are adapted to engage respective index notches in the sprinkler body as the insert body is rotated to the plural operating positions.