A sawed-off shotgun (US, CAN) also called a sawn-off shotgun (UK, IRL, AU, NZ) and a short-barreled shotgun (SBS) (U.S. legislative terminology), is a type of shotgun with a shorter gun barrel—typically under 18 inches—and often a shortened or absent stock. Despite the colloquial term, barrels do not, strictly speaking, have to be shortened with a saw. Barrels can be manufactured at shorter lengths as an alternative to traditional, longer barrels. This makes them easier to transport due to their smaller profile and lighter weight. The design also makes the weapon easy to maneuver in cramped spaces, a feature sought by military close quarters combat units, law enforcement SWAT team users, and home defense purposes. With modern pump action/magazine tube shotguns, the shorter barrel limits the magazine capacity of the weapon due to the magazine tube protruding beyond the barrel. Therefore, the magazine tubes are matched in length to the barrel, which causes a reduction in the number of shells that can be held in the magazine tube.
In the 1930s, the United States, Britain and Canada mandated that a proper permit be required to own these firearms. They are subject to legal restrictions depending upon jurisdiction. They also are in use by military forces and police agencies worldwide.
Compared to a standard shotgun, the sawn-off shotgun has a shorter effective range, due to a lower muzzle velocity and wider spread of shot. Despite these drawbacks, its reduced size makes it easier to maneuver and conceal. Powerful and compact, the weapon is especially suitable for use in small spaces, such as close quarters combat in a military context. Military vehicle crews use short-barreled combat shotguns as ancillary weapons. In urban combat zones, military entry teams often use entry shotguns when breaching and entering doorways.
To make shotguns less concealable, many jurisdictions have a minimum legal length for shotgun barrels. These restrictions are aimed at making concealable shotguns not available to criminals who might intend to use the weapons in the commission of robberies or other crimes. Most gun makers in the U.S. have not offered sawed-off shotguns to the public since the early 1900s, when shotguns with barrel lengths of under 18" were restricted, although they had been offered prior to that time without being illegally modified. Currently, aftermarket companies and Special Occupational Taxpayers exist that legally convert most name brand shotguns into such weapons, upon payment of either a $200.00 or $5.00 Federal fee for transferring ownership.
A sawed-off shotgun is often an unofficial modification of a standard shotgun. In countries where handguns are more costly or difficult to obtain, criminals might convert legally purchased or stolen shotguns into concealable weapons. For criminal organizations, the easy availability of standard hunting ammunition is another advantage of sawed-off shotguns. This practice is not limited to localities where handguns are difficult to obtain. Sawed-off shotguns might be made for a number of reasons, such as the reputation they have gained through portrayal in action movies and news reports of crime incidents.
The term is often applied to illegal weapons that are created by cutting off the barrel of a standard shotgun. This has a dramatic effect on double-barreled or single-shot shotguns because the barrel can be cut to any length. Pump-action or semi-automatic shotguns usually have a tube magazine attached to the underside of the barrel which limits the minimum barrel length to slightly longer than the length of the magazine tube, when only the barrel is modified. Although the magazine can be shortened, with a corresponding loss in magazine capacity, such a modification tends to be considerably more technically complex, involving cutting and welding or silver soldering at a bare minimum and often large diameter square threading. Repeating-fire shotguns with box magazines do not lose shell capacity when sawed off, but they are far less common than those with tubular magazines. Shotguns manufactured with barrels under the legal minimum length frequently fall into special categories.
Many nations have placed legal restrictions on sawed-off shotguns. The following are the restrictions for specific nations.
A shotgun may not have its barrel shortened so as to change the category under which that shotgun would be classified. In some states, any alteration to the length of the barrel requires permission from the Chief Commissioner of Police.
Short-barreled, manually operated shotguns (non-semi-automatics) are non-restricted as long as the barrel remains unmodified from the original factory length. There is no legal minimum for shotgun barrels as long as they are not handguns, and so shotguns with barrels as short as 8.5 inches are available in Canada.  
Despite this, the act of reducing the barrel of a shotgun with a greater than 470 mm (18.5 inch) barrel below this length by sawing, cutting, or "otherwise" (by anyone other than a recognized gun manufacturer) is prohibited.
Short barreled shotguns are universally category B weapons and therefore require a shall issue permit and Gun license (zbrojní průkaz), including the self defense category.
In Germany, the possession of a sawed-off shotgun is legal with a firearms license (Waffenbesitzkarte), just like any other firearm. Restrictions only apply to pump-action shotguns, which require a minimum barrel length of 45 cm and a minimum overall length of 90 cm to be legal. These restrictions only apply to pump-action shotguns, all others are legal to possess in any length. If the barrel length is less than 30 cm or the overall length is less than 60 cm, the firearm is considered a handgun, and treated accordingly under the law.
Shortening the barrel of a shotgun or rifle results in a presumptive five year minimum sentence of imprisonment upon conviction for a first offence, and a mandatory five-year sentence for second or subsequent offences.
Within the United Kingdom, side-by-side, over-under, bolt action and lever action shotguns are required to conform to the specification of a 24" minimum barrel length if held on a shotgun certificate. If held on a firearms certificate (the applicant having demonstrated 'good reason' for possession), they must comply with the standard configuration of 12" minimum barrel length, 24" minimum overall length, common with other Section 1 firearms.
Shotguns held on a shotgun certificate must either have no magazine, or a non-removable magazine capable of holding no more than two rounds. Shotguns held on firearms certificates are not subject to any magazine restrictions.
Semi-automatic and pump action shotguns, regardless of whether they are held on shotgun or firearms certificates are always required to comply with the specification of 24" minimum barrel length, 40" minimum overall length.
Muzzleloading firearms held on firearms certificates are exempt from any restrictions on barrel and overall length. A smoothbore muzzleloader held on a shotgun certificate would be subject to the standard 24" minimum barrel length specification.
Under the National Firearms Act (NFA), it is illegal for a private citizen to possess a sawed-off modern smokeless powder shotgun (a shotgun with a barrel length shorter than 18 inches (46 cm) or an overall length shorter than 26 inches (66 cm)) (under U.S.C. Title II), without a tax-paid registration from the Bureau of Alcohol, Tobacco, Firearms and Explosives, requiring a background check and either a $200 or $5 tax for every transfer, depending upon the specific manufacturing circumstances of the particular sawed-off modern shotgun being transferred. Gun trusts have become an increasingly popular means of registering SBS' with the BATFE. Short-barreled muzzleloading blackpowder shotguns, in contrast, are not illegal by federal law and require no tax-stamped permit, although they may be illegal under state law. As with all NFA regulated firearms, a new tax stamp must be purchased before every transfer. Inter-state transfers must be facilitated through a Federal Firearms Licensee (FFL) while intrastate transfers may be between two persons.
In the US, shotguns originally manufactured without shoulder stocks (and thus not legally shotguns), with a total length under 26 inches, are classified as an "Any Other Weapon" by the BATFE and have a $5 transfer tax, if they are manufactured by a maker possessing the appropriate Class 2 Special Occupational Taxpayer Federal Firearms License. In order to convert an existing shoulder-stocked shotgun to a short-barreled shotgun or an existing pistol-grip-only shotgun to an "Any Other Weapon", a private citizen must pay the standard $200 NFA tax.
Additional restrictions might apply in many other jurisdictions. State and local laws might entirely prohibit civilian possession of short-barrelled shotguns. (These restrictions do not apply to military and police departments.) In addition, some firearm types that would normally be considered to fall into the Short Barrel Shotgun (SBS) category are not legally considered to be a SBS. A shotgun is legally defined as a shoulder-mounted firearm that fires shot. Shotguns and shotgun receivers that have never had a buttstock of any type installed are not shotguns, as they cannot be shoulder mounted. Therefore, cutting one of these below the 18" barrel and/or 26" overall length cannot produce a SBS as the firearm was never a shotgun. The Bureau of Alcohol, Tobacco, Firearms & Explosives recognizes these firearms as being a smooth bore handgun which is an Any Other Weapon (AOW). Unlike an SBS, an AOW only carries a $5.00 tax and can be moved interstate without Federal approval. To maintain its AOW status, it must not have a buttstock (making it a SBS) or a rifled slug barrel (making it a Destructive Device (DD) if the bore is over 0.5"). Firearms of this type are typically over 100 years old. These weapons produced with a barrel length under 18" are not considered sawed-off shotguns because they were not produced with a shoulder buttstock. Weapons with these specifications fall under the category of smooth bore handguns produced in heavy rifle calibers and 12/20 gauge shotgun calibers, contrary to illegal sawn-off shotguns and are not considered destructive devices. Any firearms capable of shooting shotgun style cartridges produced after the 18" minimum barrel restrictions were set into place are considered illegal sawed-off shotguns.
Historical military use of sawed-off shotguns includes use as a primary weapon for Confederate cavalry during the American Civil War. These muzzle-loaded weapons were used primarily for close-range combat and to supplement the availability of more traditional short ranged weapons such as the saber or carbine. The availability of the source weapons and the ability to use single ball, shot, or a mix of both as the situation required were reasons why they were initially desired by those establishing Confederate cavalry units. They were replaced over time as more conventional arms became available and as the tactical use of cavalry shifted towards use as mounted infantry.
In modern usage, minimum length and barrel length restrictions only apply to civilian use; military and police departments may issue short-barreled shotguns, and major manufacturers offer special models with barrels in the range of 10 to 14 inches (25 to 36 cm) as riot shotguns or combat shotguns for use in areas with restricted space. These are generally referred to as "entry shotguns", because they are generally used for entering buildings, where the short easy handling is more important than the increased ammunition capacity of a longer shotgun. Breaching rounds provide another use for very short shotguns. These rounds are usually made of sintered powdered metal, but a normal buckshot or bird shot round will also work. A shotgun is used for breaching by placing the gun next to a door lock (0 to 2 inches away, 0 to 5 cm), and firing at a 45 degrees downward angle through the door between the lock or latch and the door frame. The impact of the projectile(s) opens a hole through the door, removing the latch or locking bolt. When through the door, the shot or sintered metal disperses quickly, and because it was aimed downwards, the risk of harming occupants on the other side of the breached door is minimized. Breaching guns used by police and the military may have barrels as short as 10 inches (25 cm), and they often have only a pistol grip rather than a full butt stock. Some models use a special cup-like muzzle extension to further minimize the risk of debris injuring the shooter. Because few rounds are fired, any sporting shotgun with a 3-round capacity could be shortened and used as a capable breaching shotgun.
It is a common misconception that shortening the length of a shotgun barrel itself significantly affects the pattern or spread of the pellets; this is not true until barrel length is decreased to under 50% of a typical barrel length. A standard length barrel (e.g., 28") is this long to move the center of gravity of the weapon away from the body and give it an ergonomic heft, and in order for the barrel to extend out into the shooter's field of vision right up to the target, as well as to make the weapon more safe as it is very difficult to inadvertently point a long gun at one's own body. The pattern is primarily affected by the type of cartridge fired and the choke, or constriction normally found at the muzzle of a shotgun barrel.
The primary reason that the pattern is altered is because cutting off the end of the barrel removes the choke, which generally only extends about two inches (about 5 cm) inward from the muzzle. This results in a cylinder bore, which causes the widest spread generally found in shotgun barrels. (See choke for more information on the impact of chokes. See shotgun shell for information on spreader loads.) See details on shot patterning.
In the United Kingdom, Australia, Canada and New Zealand, where handguns are not easily obtainable, the sawn-off shotgun was a common weapon in armed robberies during and shortly after the 1960s, and it is this use that most people associate with the weapon.
A sawn-off shotgun with exposed, manually-cocked hammers and dual triggers is known as a lupara ("wolf-shot") in Italy, and while associated with organized crime, was originally used by Sicilian farmers and shepherds to protect their vineyards and flocks of animals. In rural areas of North India, where it is seen as a weapon of authority and prestige, it is known as a dunali, literally meaning "two pipes". It is especially common in Bihar, Purvanchal, Uttar Pradesh, Haryana and Punjab.
The bank robber Clyde Barrow modified his Browning A-5 shotgun by cutting the barrel down to the same length as the magazine tube, and shortening the stock by 5 to 6 inches (125 to 150 mm) to make it more concealable. A small, 10–12-inch (250–300 mm) strap was attached to both ends of the butt of the gun, and was looped around his shoulder, concealing the gun between his arm and chest under his jacket in the manner of a shoulder holster. The gun was drawn up quickly and fired from the shoulder under which it was carried. Barrow dubbed it the "Whippit", as he was able to "whip it" out easily.
The light weight of short-barreled shotguns, particularly in configurations that lack substantial stocks, leads some users to use short 'minishells' with lower shot and powder loading for comfortable casual use.