caliber rimfire ammunition. United States In the US, federal law prohibits shotguns from being capable of holding more than three shells including the round in the chamber when used for hunting migratory gamebirds such as doves, ducks, and geese. For other uses, a capacity of any number of shells is generally permitted. Most magazine-fed shotguns come with a removable magazine plug to limit capacity to 2, plus one in the chamber, for hunting migratory gamebirds. Certain states have restrictions on magazine capacity or design features under hunting or assault weapon laws. Shotguns intended for defensive use have barrels as short as for private use (the minimum shotgun barrel length allowed by law in the United States without federal registration. Barrel lengths of less than as measured from the breechface to the muzzle when the weapon is in battery, or have an overall length of less than are classified as short barreled shotguns (SBS) under the 1934 National Firearms Act and are regulated. A similar short barreled weapon having a pistol grip may be classified as an AOW or "Any Other Weapon" or "Firearm," depending on barrel length. A shotgun is defined as a weapon (with a buttstock) designed to be fired from the shoulder. The classification varies depending on how the weapon was originally manufactured. Shotguns used by military, police, and other government agencies are regulated under the National Firearms Act of 1934; however, they are exempt from transfer taxes. These weapons commonly have barrels as short as so that they are easier to handle in confined spaces. Non-prohibited private citizens may own short-barreled shotguns by passing extensive background checks (state and local laws may be more restrictive) as well as paying a $200 federal tax and being issued a stamp. Defensive shotguns sometimes have no buttstock or will have a folding stock to reduce overall length even more when required. AOWs transfer with a $5 tax stamp from the BATFE. See also Antique guns Gun safety List of shotguns Double-barreled shotgun Riding shotgun Shotgun wedding Military 12-gauge cartridges Mare's Leg Shotgun (shooting sports) References Notes Bibliography External links Shotgun FAQ Shotgun sabot separation photography "Shotgun Chokes and Gauges." Popular Mechanics, October 1947, p. 196–200. Excellent diagrams and drawings.