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A shotgun is a firearm typically used to fire a number of small balls, the shot, from a smoothbore barrel of relatively large diameter. Also the bullets that are shot can be spread into many small balls. The energy of any one ball of shot is fairly low, making them useful primarily for hunting birds and other small game, or as close-combat weapons where the short range ensures that many of the balls of shot will hit the target.
The United States legal code (18 USC 921) defines the shotgun as "a weapon designed or redesigned, made or remade, and intended to be fired from the shoulder, and designed or redesigned and made or remade to use the energy of the explosive in a fixed shotgun shell to fire through a smooth bore either a number of ball shot or a single projectile for each single pull of the trigger." United Kingdom law requires that a shotgun not be capable of holding more than three rounds; if it holds more it is classed as a firearm. In the United States, shotguns which have barrel lengths of less than 18 inches (45.72 cm) as measured from the breechface to the muzzle when the weapon is in battery with its action closed and ready to fire, or have an overall length of less than 26 inches (66.04 cm) are classified as short barreled shotguns (AKA " sawn-off shotguns") under the National Firearms Act of 1934 and heavily regulated.
This definition, however, does not exactly match the technical use of the term, which would include the growing number of shotguns specifically designed to fire single projectiles instead of shot. Rifled slugs, which have fins or rifling on or behind the bullet designed to spin the bullet and stabilize it (in order to improve its accuracy), is an example of a single projectile. Some shotguns have rifled barrels and are designed to be used with a "saboted" bullet. A saboted bullet is typically encased in two-piece plastic ring and the plastic is designed to fall away after it passes the end of the barrel, leaving the bullet to continue toward the target while twisting (from passing through the rifled barrel) to keep its trajectory, though it can also be as low-tech as an old trick Finnish hunters used during the Great Depression--prying open the crimped top of a shotgun cartridge, pouring out the shot, and inserting a single large steel ball bearing, just slightly smaller than the diameter of the gun's bore, wrapped in paper so that it won't rattle side to side as it goes through the barrel. These shotguns, although they have rifled barrels, still use a shotgun-style shell instead of a rifle cartridge. Hunting laws may differentiate between smooth barreled and rifled barreled guns.
Also, technically speaking, many people would likely call a fully automatic shotgun a shotgun, even though legally it would fall under a different category.
There are many types of shotguns, typically categorized by the number of barrels or the way the gun is reloaded. For most of the history of the shotgun, two barrels were used to allow for two shots, known as the double barreled shotgun. In this case there are several "subtypes", the over and under shotgun puts the two barrels one on top of the other, while the side-by-side shotgun puts them beside each other.
Semi-automated loading systems are also available. A small number of guns are available with a bolt action, but far more common is the pump action shotgun, in which a sliding handle, the pump, works the action to reload the single barrel. Some shotguns, such as the Franchi SPAS-12SPAS-12 Technical Summary Caliber: 12 gauge Action: Pump-action/ gas-actuated Weight: 4. 7 lb) Length: 1041 mm (41 in) Barrel length: 546 mm (22 in) Magazine: 8+1 rounds, internal The SPAS-12 is a dual-mode 12 ga. shotgun manufactured by the Italian compa and Benelli M3, are capable of switching between semi-automatic and pump action.
Some of the more interesting advances in shotgun technology include the versatile NeoStead 2000The NS2000 is a type of shotgun developed for the South African company NeoStead by Tony Neophytou. It, along with the Pancor Jackhammer, is considered one of the most technologically advanced shotguns created. The NS2000 has been used in trial runs for a and fully automatics such as the Pancor JackhammerThe Pancor Corporation Jackhammer is a combat shotgun. It is a 12 gauge, gas-operated automatic weapon. With its stylish design, it is one of very few fully automatic shotguns. Patented in 1987 it has not entered full scale production, although its distin. These combat shotgunCombat shotguns shotguns modified slightly to increase their suitability for use in combat, have been popular in the United States, both with law enforcement and with the US military (particularly the US Marine Corps), since the 19th Century. The most coms while popular in movies and computer games due to their exotic nature, have yet to make a noticeable impression in the real world.
The caliber of shotguns is measured in terms of gauge or bore. The gauge number is determined by the number of solid spheres of a diameter equal to the inside diameter of the barrel that could be made from a pound of lead. So a 10 gauge shotgun has the inside diameter equal to that of a sphere made from one-tenth of a pound of lead. By far the most common gauges are 12 (0.73" diameter, 18.5mm) and 20 (0.614", 15.6mm), although 4, 8, 10, 14, 16, 24, 28, 32 gauges and the .410 calibre have also been produced larger gauge have been built but are general called punt guns . (The .410 calibre is measured in inches instead of gauge for historical reasons. The .410 calibre, approximately 67 gauge, was created to impose maximum handicap upon skilled shooters in games like skeet and trap, by throwing a relatively small charge of shot. The .410 calibre was not created for hunting, but some people do use it for that.)
Despite the above mention of slugs and sabots most shotguns are used to fire "a number of ball shot". The ball shot or pellets is for the most part made of lead but this has been partially replaced by bismuth, steel, tungsten-iron, tungsten-nickel-iron and even tungsten polymer loads. Non-toxic loads are required by Federal law for waterfowl hunting in the US, as the shot may be ingested by the waterfowl, which some authorities believe can lead to health problems due to the lead exposure. Shot is termed either birdshot or buckshot depending on the shot size. Informally birdshot pellets have a diameter smaller than 0.20 inches and buckshot larger. Pellet size is indicated by a cartridge number, for birdshot this ranges from the smallest 12 (0.05") to 2 (0.15") and then BB (0.18"), for buckshot the numbers usually start at 4 (0.24") and go down to 1, 0, 00 and finally 000 (0.36"). A different informal distinction is that "birdshot" pellets are small enough that they can be measured into the cartridge by weight, and just poured in, whereas "buckshot" pellets are so large that they won't all fit unless they're stacked inside the cartridge one by one in a certain particular geometric arrangement; by this definition, #4 buckshot, 0.24" in diameter (6.3mm) is buckshot because the pellets have to be stacked in a certain arrangement inside the cartridge or else they won't all fit, but anything smaller can be measured by weight and just dumped in.
As the shot leaves the barrel there is a "puff" of gunpowder that can push the shot sideways, thereby spreading out the pattern of shot. To combat this problem most shotgun barrels come with a system known as a choke, a constriction near the end that directs the flow of gases and thereby keeps the shot in a tight pattern. In increasing order of constriction: Improved (or 1/4), Modified (or 1/2), Improved Modified (or 3/4), and Full choke. Each increment of choke is just a few hundredths of an inch. "Cylinder barrels" have no constriction. See also: Slug barrelA slug barrel is a barrel for a shotgun that is designed primarily to shoot slugs. Until widespread use of the sabot slug starting in about 1985, most slug barrels were un rifled, having a smooth bore. They differed from standard shotgun barrels by the ab