Single action refers to a firearm in which the trigger performs only a single action: to release the cocked hammer or striker. If it isn't cocked, nothing happens when the trigger is pulled. A single action revolver must be manually cocked between each firing.In a double action revolver, the trigger performs both the act of cocking and of releasing the hammer or striker. This means that the piece will fire every time the trigger is pulled, although the trigger pull becomes longer.
