An apparatus for locking an inner telescoping member into a desired position within an outer telescoping member or sleeve. A locking mechanism is carried by the inner telescoping member and includes locking pins supported for motion between respective retracted positions and respective extended positions engaging detents in the outer telescoping member. A synchronizing ring is operatively connected to the locking pins such that synchronizing ring rotation moves the locking pins between the locking pins' respective retracted and extended positions.