The tracer gun, sometimes known as a disc gun, is a kind of toy gun made of plastic. The toy shoots lightweight plastic discs roughly the size of a small coin. The discs used as ammunition for these guns are often sold with the label 'Jet Discs.' The firing mechanism is a spring, which can be modified to make the gun shoot farther. The magazine holds 20 discs. Range is about 10 feet, and even then, accuracy is far from dependable. The trigger requires some force. The firing sound is loud, low, and distinctive, akin to a taut rubber band snapping on a cardboard box.
The gun was manufactured starting in the 1960s. Older guns come in a variety of colors including dull bronze or bluish silver plastic, but more recent models are usually made in bright colors to distinguish them from real weapons. The brightly-colored models are usually manufactured in China. Many of the older bronze and blue guns were made by in the United States Ray Plastics, Inc. under the brand name "Rayline," including a collectible Star Trek version. The Star Trek version was first made in 1966 and is one of the earliest Star Trek licensed products. A rifle version of the tracer gun was also made. The toy, including the Star Trek version, was sold in Canada under the Grand Toys brand.
Tracer guns have often been used to play a game popular at high schools and colleges known as "Killer," "Killer Tag" or "Killer Assassination" that involves trying to "assassinate" the other players with toy weaponry. Tracer guns suit this kind of game well because they are cheap and easily obtainable, and their bright colors and low firing power (often, a target does not even know a shot has hit) help to address safety issues.