The double action trigger is based on the single action trigger. The difference is that with the double-action trigger, which is also called a cocking trigger, when the trigger is pulled, first the hammer is cocked and then, if the pulling movement is continued, the shot breaks. With the single-action trigger, it is not possible to shoot solely by pulling the trigger, the hammer must first be cocked, in a separate movement. In revolvers, cocking the hammer automatically causes the barrel to continue rotating.