Shotgun

:This article is about the firearm. For alternative meanings of shotgun, see: Shotgun (disambiguation).

Design factors

Action

Action is the term for the operating mechanism of a gun. 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, the breech loading double barreled shotgun, with two barrels, was the most common type. 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. Another class of break open shotgun is the combination gun, which is an over and under design with one shotgun barrel and one rifle barrel (more often rifle on top, but rifle on bottom was not uncommon). There is also a class of break action guns called drillings, which contain three barrels, usually 2 shotgun barrels of the same gauge and a rifle barrel, though the only common theme is that at least one barrel be a shotgun barrel. The most common arrangement was essentially a side by side shotgun with the rifle barrel below and centered. Usually a drilling containing more than one rifle barrel would have both rifle barrels in the same caliber, but examples do exist with different caliber barrels, usually a .22 Long Rifle and a centerfire cartridge. Although very rare, there were some three shotgun barrel drillings made.

Related Topics:
Double barreled shotgun - Over and under shotgun - Side-by-side shotgun - Rifle - Caliber - .22 Long Rifle - Centerfire

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Non break open designs use a single barrel, and are magazine fed. In pump-action shotguns, a sliding forearm handle, the pump, works the action to reload the single barrel. Lever action guns, while less common, were popular in the late 1800s. Gas, inertia, or recoil operated actions are other popular methods of increasing the rate of fire of a shotgun; these actions are generally referred to as autoloaders or semi-automatic shotguns. A small number of guns are available with a bolt action, but this is uncommon. Some shotguns, such as the Franchi SPAS-12 and Benelli M3, are capable of switching between semi-automatic and pump action.

Related Topics:
Pump-action shotguns - 1800s - Franchi SPAS-12 - Benelli

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Some of the more interesting advances in shotgun technology include the versatile NeoStead 2000 and fully automatics such as the Pancor Jackhammer. These combat shotguns, while popular in movies and computer games due to their exotic nature, have yet to make a noticeable impression in the real world.

Related Topics:
NeoStead 2000 - Pancor Jackhammer - Combat shotgun

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Gauge

The caliber of shotguns is measured in terms of gauge or bore (the British English term). 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 an 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 in, 18.5 mm diameter) and 20 (0.614 in, 15.6 mm), although 2, 4, 8, 10, 14, 16, 24, 28, 32 gauges and .410 (10 mm) 9mm (.355 in.) rimfire and .22 (5.5 mm) rimfire calibres have also been produced. To further complicate matters, typical handgun chamberings such as 9 mm Luger, .45 ACP, .38 Special/.357 Magnum, .44 Special/.44 Magnum, and .45 Colt have been brought to market by CCI/Speer and others bearing a "shot" load--either crimped in or in a plastic casing that takes the place of the bullet. These are not generally considered "shot shells" by shotgun users, and the patterning performance is questionable since they are fired through rifled barrels. Thompson/Center makes special pistol barrels in .38/357, .44 and .45 Colt that have "straight rifled" chokes in them to reduce the spin of the shot column and produce better patterns, but they are still suitable only for pest control at very short ranges. Larger gauges, too powerful to shoulder, have been built but were generally affixed to small boats and referred to as punt guns. These were used for water fowl hunting, to kill large numbers of birds resting on the water. Although relatively rare, single-shot and two-shot derringers have also been produced that are capable of firing both .45 Colt (also known as 45 Long Colt) and .410 shotgun shells in the same chamber; they are commonly known as 'snake guns', and are popular among some outdoorsmen in the South and Southwest regions of the United States.

Related Topics:
Rimfire - Handgun - 9 mm Luger - .45 ACP - .38 Special - .357 Magnum - .44 Special - .44 Magnum - .45 Colt - CCI/Speer - Pistol - Punt gun - Water fowl

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The .410 calibre (10 mm) is measured in inches instead of gauge for historical reasons. The .410 calibre (10 mm), approximately 67 gauge, was created to impose maximum handicap upon skilled shooters in the game of skeet, by throwing a relatively small charge of shot. The .410 calibre (10 mm) was not created for hunting, but some people do use it for that, especially in bolt-action .410 shotguns. It is a very common first hunting shotgun among young pre-teen hunters, where it is used mostly for hunting squirrels. Most of these young hunters move up to 20 gauge shotguns within a few years, before moving on up to 12 gauge shotguns by their late teenage years.

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Shot

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 bird shot or buckshot depending on the shot size. Informally, bird shot pellets have a diameter smaller than 0.20 inches (5 mm) and buckshot larger. Pellet size is indicated by a number, for bird shot this ranges from the smallest 12 (0.05 in) to 2 (0.15 in) and then BB (0.18 in), for buckshot the numbers usually start at 4 (0.24 in) and go down to 1, 0, 00 and finally 000 (0.36 in). A different informal distinction is that "bird shot" 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. The diameter in hundredths of inches of bird shot sizes from #9 to #1 can be obtained by subtracting the shot size from 17. Thus, #4 bird shot is 17 - 4 = 13 = 0.13 inches (3.3 mm) in diameter. Different terminology is used outside the United States. In England and Australia, for example, 00 buckshot cartridges are commonly referred to as "S.G." (small game) cartridges.

Related Topics:
United States - England - Australia

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Pattern and choke

Shot, small and round and delivered without spin, is ballistically inefficient. As the shot leaves the barrel it begins to disperse in the air. The resulting cloud of pellets is known as the shot pattern. The ideal pattern would be a circle with an even distribution of shot throughout, with a density sufficient to ensure enough pellets will intersect the target to achieve the desired result, such as a kill when hunting or a break when shooting clay targets. In reality the pattern is closer to a Gaussian, or normal distribution, with a higher density in the center that tapers off at the edges. Patterns are usually measured by firing at a 30 inch (76 cm) diameter circle on a larger sheet of paper placed at varying distances. The hits outside the circle are counted, and compared to the total number of pellets, and the density of the pattern inside the circle is examined. An "ideal" pattern would put nearly 100% of the pellets in the circle, and would have no voids--any region where a target silhouette will fit and not cover 3 or more holes is considered a potential problem.

Related Topics:
Pattern - Gaussian

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A constriction in the end of the barrel known as the choke is used to tailor the pattern for different purposes. Chokes may either be formed as part of the barrel at the time of manufacture, by squeezing the end of the bore down over a mandrel, or by threading the barrel and screwing in an interchangeable choke tube. The choke typically consists of a conical section that smoothly tapers from the bore diameter down to the choke diameter, followed by a cylinderical section of the choke diameter. Briley Manufacturing, a top maker of interchangeable shotgun chokes, uses a conical portion about 3 times the bore diameter in length, so the shot is gradually squeezed down with minimal deformation. The cylindrical section is shorter, usually 0.6 to 0.75 inches (15 to 19 mm). There is no good mathematical model that describes how chokes work, making the design and manufacture for chokes more art than science. The use of interchangeable chokes has made it easy to tune the performance of a given combination of shotgun and shotshell to achieve the desired performance.

Related Topics:
Choke - Mandrel

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The choke should be tailored to the range and size of the targets. A skeet shooter, shooting at close targets might use 0.005 inches (127 micrometres) of constriction to produce a 30 inch (762 mm) diameter pattern at a distance of 21 yards (19 m). A trap shooter, shooting at distant targets might use 0.030 inches (762 micrometres) of constriction to produce a 30 inch (762 mm) diameter pattern at 40 yards (37 m). Special chokes for turkey hunting, which requires long range shots at the small head and neck of the bird, can go as high as 0.060 inches (1520 micrometres). The use of too much choke and a small pattern increases the difficulty of hitting the target, the use of too little choke produces large patterns with insufficient pellet density to reliably break targets or kill game. "Cylinder barrels" have no constriction. See also: Slug barrel

Related Topics:
Skeet - Trap - Slug barrel

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Other specialized choke tubes exist as well. Some turkey hunting tubes have constrictions greater than "Super Full", or addittional features like porting to reduce recoil, or "straight rifling" that is designed to stop any spin that the shot column might acquire when traveling down the barrel These tubes are often extended tubes, meaning they project beyond the end of the bore, giving more room for things like a longer conical section. Shot spreaders or diffusion chokes work opposite of normal chokes--they are designed to spread the shot more than a cylinder bore, generating wider patterns for very short range use. Oval chokes, designed to provide a shot pattern wider than it is tall, are sometimes used in combat shotguns. Offset chokes, where the choke is intentionally made slightly off of center, are also made, and are used to change the point of impact; for instance, an offset choke can be used to make a double barrelled shotgun with poorly aligned barrels hit the same spot with both barrels.

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Barrel length

Shotguns generally have longer barrels than modern rifles. Unlike rifles, however, the long shotgun barrel is not for ballistic purposes; shotgun shells use small powder charges in large diameter bores, and this leads to very low muzzle pressures (see internal ballistics) and very little velocity change with increasing barrel length.

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According to Remington, modern powder in a shotgun burns completely in 10-14-inch barrels.

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Since shotguns are generally used for shooting at small, fast moving targets, it is important to lead the target by firing slightly ahead of the target, so that when the shot reaches the range of the target, the target will have moved into the pattern. Shotguns made for close ranges, where the angular speed of the targets is great (such as skeet shooting, or upland bird hunting) tend to have shorter barrels, around 24 to 28 inches (610 to 710 mm). Shotguns for longer range shooting, where angular speeds are less (trap shooting and waterfowl hunting) tend to have longer barrels, 28 to 34 inches. The longer barrels have more inertia, and will therefore swing slower but steadier. The short, low inertia barrels swing faster, but are less steady. These lengths are for pump or semi-auto shotguns; break open guns have shorter overall lengths for the same barrel length, and so will use longer barrels. The break open design saves between 3.5 and 6 inches (90 and 150 mm) in overall length, but in most cases pays for this by having two barrels, which adds weight at the muzzle, and so usually only adds a couple of inches (50 mm). Barrels for shotguns have been getting longer as modern steels and production methods make the barrels stronger and lighter; a longer, lighter barrel gives the same inertia for less overall weight.

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Shotguns for use against larger, slower targets generally have even shorter barrels. Small game shotguns, for game like rabbits and squirrels, or shotguns for use with buckshot for deer, are usually 22 to 24 inches (560 to 610 mm). Shotgun intended for defensive use are as short as 18 inches (457 mm) for civilian use (the minimum shotgun barrel length allowed by law in the United States). Military and police shotguns, which are not regulated by law, often have barrels as short as 12 to 14 inches (305 to 356 mm), so that they are easier to handle in confined spaces. Defensive shotguns will often have no buttstock or a folding stock to reduce overall length even more.

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