A pneumatic actuator having therein a venting element and a porous element, compression and elongation of the actuator creating an air flow in the venting element and porous element to output lubricant as a mist toward a sliding interface of the actuator. A bow using the actuator and a bow having a double string preventing sideward movement when launching an arrow. A compound bow having limbs with multiple rotatable elements and an actuator rotating such elements to launch an arrow.