A coach gun is a modern term, coined by gun collectors, for a double-barreled shotgun, generally with barrels from 18" to 24" in length placed side-by-side. These weapons were known as "cut-down shotguns" or "messenger's guns" from the use of such shotguns on stagecoaches by shotgun messengers in the American Wild West. They came in 10 and 12 gauge blackpowder.
Origins
The terms "cut-down shotgun" or "messenger's gun" were coined in the 1860s when Wells Fargo & Co. assigned shotgun messengers to guard its shipments on stagecoaches in California. The company issued shotguns to its guards for defense. The guard was called a shotgun messenger although the phrase riding shotgun was not coined until 1919. Shotgun messengers guarded express shipments, not stagecoaches. There was no single manufacturer for the traditional messenger's gun, as it was a generic term describing a class of shotguns offered in a variety of barrel lengths from , either by the factory or from owners and gunsmiths cutting down the barrels.
Early manufacturers
These shotguns featured external hammers and were manufactured primarily by Remington Arms, Ithaca, Colt's Manufacturing Company, Parker, L.C. Smith, and several Belgian makers. Contrary to myth, Wells Fargo shotguns were not purchased by local agents; prior to 1900 they were purchased from San Francisco gun dealers because Wells Fargo's headquarters were located in San Francisco. From 1908 to 1918 all Wells Fargo shotguns were made by Ithaca.
Modern coach guns are commonly encountered in Cowboy Action Shooting competitions, among collections of Western guns, as home-defense weapons, and even as "scrub guns" for huntinggrouse, woodcock, rabbit, hare, and/or wild pig in scrub, bush or marshlands, where the 24"+ barrels of a traditional shotgun would prove unwieldy. The modern coach gun can be had in a variety of configurations suitable for both Cowboy Action Shooting competition and hunting. Coach guns are similar to sawn-off shotguns but differ in that coach guns manufactured after 1898 are offered as new with 18" barrels and 26" overall length and meet legal requirements for civilian possession in the United States. Australia and New Zealand have slightly different laws for length, with NZ requiring a minimum overall length of 30" with no minimum barrel length and Australia requiring an 18" barrel and a 30" overall length. In the United Kingdom, however, shotguns must have a minimum barrel length of 24" to be eligible for ownership on a Shotgun Certificate, and shotguns with barrels under this length must be obtained on the more stringent Firearms Certificate. Some modern coach guns feature internal hammers as opposed to the traditional external hammers.
Legacy
It is because of this gun and its usage that the term "Riding shotgun" came to be. Typically, a cut-down shotgun would be carried by the messenger sitting next to the stagecoach driver, ready to use the gun to ward off bandits. Today, in American and Canadian English, the term "Riding shotgun" refers to the person sitting in the front passenger seat of an automobile.