Helical spline actuators can be employed to actuate ball valves. In certain embodiments, an actuator can include a remote operated vehicle shaft, an internally splined shaft, and an externally splined shaft that can be used in combination to actuate a ball valve. In certain embodiments, an actuator can include a piston that is displaced axially and not rotated, an externally splined shaft, and an internally splined shaft that can be used in combination to actuate a ball valve. In certain embodiments, an actuator can include a piston, a spring, a spring cap, and a joint member wherein the spring cap and joint member translate axial force from the spring to the piston. In certain embodiments, an actuator can include a bearing that insulates a piston from rotational forces exerted by an externally splined shaft.