<P> A backpacker shotgun has a short barrel and either a full - size stock or pistol grip, depending on legislation in intended markets . The overall length of these weapons is frequently less than 90 cm (35 in), with some measuring up at less than 63 cm (25 in). These weapons are typically break - action . 410 "gauge" (caliber), single - barrel designs with no magazine and no automatic ejection capability . They typically employ a cylinder bore and sometimes are available in modified choke as well . </P> <P> Backpacker shotguns are popular for "home defense" purposes and as "survival" weapons . Other examples include a variety of . 410 / rifle "survival" guns manufactured in over / under designs . In the drilling arrangement, a rimfire or centrefire rifle barrel is located beneath the barrel of a . 410 gauge shotgun . Generally, there is one manually cocked external hammer and an external selection lever to select which caliber of cartridge to fire . A notable example is the Springfield Armory M6 Scout, a . 410 / . 22 issued to United States Air Force personnel as a "survival" gun in the event of a forced landing or accident in a wilderness area . Variants have been used by Israeli, Canadian, and American armed forces . Shotgun - rifle combination guns with two, three, and occasionally even four barrels are available from a number of makers, primarily European . These provided flexibility, enabling the hunter to effectively shoot at flushing birds or more distant small mammals while only carrying one gun . </P> <P> Most early firearms, such as the blunderbuss, arquebus, and musket had large diameter, smoothbore barrels, and could fire shot as well as solid balls . A firearm intended for use in wing shooting of birds was known as a fowling piece . The 1728 Cyclopaedia defines a fowling piece as: </P> <Dl> <Dd> Fowling Piece, a portable Fire Arm for the shooting of Birds . See Fire Arm . </Dd> <Dd> Of Fowling Pieces, those are reputed the best, which have the longest Barrel, vis. from 5 ​ ⁄ foot to 6; with an indifferent Bore, under Harquebus: Tho' for different Occasions they shou'd be of different Sorts, and Sizes . But in all,' tis essential the Barrel be well polish'd and smooth within; and the Bore all of a Bigness, from one End to another...</Dd> </Dl>

When was the first over under shotgun made