A shot timer is just what it sounds like, a timer that is activated by the actual sound of a gunshot. It's what they use in shootings sports to garner results. They typically tell the competitor to start with an audible tone. The device also records the competitor's time electronically by detecting the sound of each shot together with the time from the start signal.
But, they have more applications that judging competitions. A shot timer can be useful for recording your performance in several ways, which can make you a better shot. Handgun instructor Tom McHale shows you exactly how.