Shotgun

Shotgun

This article is about the firearm. For other uses, see Shotgun (disambiguation).

A pump-action Remington 870, two semi-automatic Remington 1100 shotguns, 20 boxes of shotgun shells, a clay trap, and three boxes of clay pigeons.

A shotgun (also known as a scattergun and pepper gun, or historically as a fowling piece) is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug. Shotguns come in a wide variety of sizes, ranging from 5.5 mm (.22 inch) bore up to 5 cm (2 inch) bore, and in a range of firearm operating mechanisms, including breech loading, single-barreled, double or Combination gun, pump-action, bolt-, and lever-action, semi-automatic, and even fully-automatic variants.

A shotgun is generally a smoothbore firearm, which means that the inside of the barrel is not rifled. Preceding smoothbore firearms, such as the musket, were widely used by armies in the 18th century. The direct ancestor to the shotgun, the blunderbuss, was also used in a similar variety of roles from self defence to riot control. It was often used by cavalry troops due to its generally shorter length and ease of use, as well as by coachmen for its substantial power. However, in the 19th century, these weapons were largely replaced on the battlefield with breechloading rifled firearms, which were more accurate over longer ranges. The military value of shotguns was rediscovered in the First World War, when American forces used 12-gauge pump action shotguns in close-quarters trench fighting to great effect. Since then, it has been used in a variety of roles in civilian, law enforcement, and military applications.

The shot pellets from a shotgun spread upon leaving the barrel, and the power of the burning charge is divided among the pellets, which means that the energy of any one ball of shot is fairly low. In a hunting context, this makes shotguns useful primarily for hunting birds and other small game. However, in a military or law enforcement context, the large number of projectiles makes the shotgun useful as a close quarter's combat weapon or a defensive weapon. Shotguns are also used for target shooting sports such as skeet, trap, and sporting clays. These involve shooting clay disks, known as clay pigeons, thrown in various ways.

 

Semi-automatic

Semi-automatic

A Browning A-5 semi-automatic shotgun

Gas, inertia, or recoil operated actions are other popular methods of increasing the rate of fire of a shotgun; these are generally referred to as autoloaders or semi-automatics. Instead of having the action manually operated by a pump or lever, the action automatically cycles each time the shotgun is fired, ejecting the spent shell and reloading a fresh one into the chamber. The first successful semi-automatic shotgun was John Browning's Auto-5, first produced by Fabrique Nationale beginning in 1902. Other well-known examples include the Remington 1100, Benelli M1, and Saiga-12.

Some, such as the Fran chi SPAS-12 and Benelli M3, are capable of switching between semi-automatic and pump action. These are popular for two reasons; first, some jurisdictions forbid the use of semi-automatic actions for hunting, and second, lower-powered rounds, like "reduced-recoil" buckshot shells and many less lethal cartridges, have insufficient power to reliably cycle a semi-automatic shotgun.

 

Lever-action

Lever-action

A modern reproduction of the Winchester M1887 lever-action shotgun

Early attempts at repeating shotguns invariably centered around either bolt-or lever-action designs, drawing inspiration from contemporary repeating rifles, with the earliest successful repeating shotgun being the lever-action Winchester M1887, designed by John Browning at the behest of the Winchester Repeating Arms Company.

Lever shotguns, while less common, were popular in the late 1800s with the Winchester Model 1887 and Model 1901 being prime examples. Initially very popular, demand waned after the introduction of pump-action shotguns at the turn of the century, and production was eventually discontinued in 1920.

One major issue with lever-actions (and to a lesser extent pump-action) was that early shotgun shells were often made of paper or similar fragile materials (modern hulls are plastic or metal). As a result the loading of shells, or working of the action of the shotgun, could often result in cartridges getting crushed and becoming unusable or even damaging the gun.

Lever shotguns have seen a return to the gun market in recent years, however, with Winchester producing the Model 9410 (chambering the .410 gauge shotgun shell and using the action of the Winchester Model 94 series lever-action rifle, hence the name), and a handful of other firearm manufacturers (primarily Norinco of China and ADI Ltd. of Australia) producing versions of the Winchester Model 1887/1901 designed for modern 12-gauge smokeless shot shells with more durable plastic casings. There has been a notable uptick in lever-action shotgun sales in Australia since 1997, when pump-actions were effectively outlawed.

Legal issues

Legal issues

A homemade Lupara

Globally, shotguns are generally not as heavily regulated as rifles or handguns, likely because they lack the range of rifles and are not easily concealable as handguns are; thus, they are perceived as a lesser threat by legislative authorities. The one exception is a sawed-off shotgun, especially a Lupara, as it is more easily concealed than a normal shotgun.

 

Gauge

Gauge

Soldier armed with a shotgun

Main article: Gauge (bore diameter)

The caliber of shotguns is measured in terms of gauge (U.S.) or bore (U.K.). The gauge number is the determined by the weight, in fractions of a pound, of a solid sphere of lead with a diameter equal to the inside diameter of the barrel. So a 10 gauge shotgun nominally should have 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 (0.729 in, 18.5 mm diameter) and 20 (0.614 in, 15.6 mm), although .410 (= 67), 32, 28, 24, 16, and 10 (19.7 mm) gauge and 9 mm (.355 in.) and .22 (5.5 mm) rimfire calibres have also been produced. 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 commercial water fowl hunting, to kill large numbers of birds resting on the water. Although relatively rare, single and double derringers have also been produced that are capable of firing either .45 (Long) Colt or .410 shotgun shells from 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. There are also some revolvers, such as the Taurus Judge, that are capable of shooting the .45LC/.410 rounds; but as with derringers, these are handguns that shoot .410 shotgun shells, and are not necessarily considered shotguns.

The .410 bore (10.4 mm) is unusual, being measured in inches, and would be approximately 67 "real" gauge, though its short hull versions are nominally called 36 gauge in Europe. It uses a relatively small charge of shot. It is used for hunting and for skeet. Because of its very light recoil (approx 10 N), it is often used as a beginners gun. However, the small charge and typically tight choke make it more difficult to hit targets. It is also frequently used by expert shooters because of the difficulty, especially in expensive side by side and over/under models for hunting small bird game such as quail and doves. Inexpensive bolt-action .410 shotguns are a very common first hunting shotgun among young pre-teen hunters, as they are used mostly for hunting squirrels, while additionally teaching bolt-action manipulation skills that will transfer easily later to adult-sized hunting rifles. Most of these young hunters move up to a 20-gauge within a few years, and to 12 gauge shotguns and full-size hunting rifles by their late teens. Still, many who are particularly recoil-averse choose to stay with 20-gauge shotguns all their adult life, as it is a very suitable gauge for many popular hunting uses.

A recent innovation is the back-boring of barrels, in which the barrels are bored out slightly larger than their actual gauge. This reduces the compression forces on the shot when it transitions from the chamber to the barrel. This leads to a slight reduction in perceived recoil, and an improvement in shot pattern due to reduced deformation of the shot.

Shot

Most shotguns are used to fire "a number of ball shot", in addition to slugs and sabots. 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 5 mm (0.20 inches) and buckshot are larger than that. Pellet size is indicated by a number, for bird shot this ranges from the smallest 12 (1.2 mm, 0.05 in) to 2 (3.8 mm, 0.15 in) and then BB (4.6 mm, 0.18 in).

For buckshot the numbers usually start at 4 (6.1 mm, 0.24 in) and go down to 1, 0, 00 ("double aught"), 000, and finally 0000 (9.7 mm, .38 in). A different informal distinction is that "bird shot" pellets are small enough that they can be measured into the cartridge by weight, and simply poured in, whereas "buckshot" pellets are so large they must be stacked inside the cartridge in a fixed geometric arrangement in order to fit. The diameter in hundredths of an inch 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.

Table of American Standard Birdshot Size
Size	Diameter	Pellets/10 g Lead	Pellets/10 g Steel
FF	5.84 mm (.230")	8	12
F	5.59 mm (.220")	10	14
TT	5.33 mm (.210")	11	16
T	5.08 mm (.200")	13	19
BBB	4.83 mm (.190")	15	22
BB	4.57 mm (.180")	18	25
B	4.32 mm (.170")	21	30
1	4.06 mm (.160")	25	36
2	3.81 mm (.150")	30	44
3	3.56 mm (.140")	37	54
4	3.30 mm (.130")	47	68
5	3.05 mm (.120")	59	86
6	2.79 mm (.110")	78	112
7	2.41 mm (.100")	120	174
8	2.29 mm (.090")	140	202
9	2.03 mm (.080")	201	290

 

Table of Buckshot Size
Size	Diameter	Pellets/10 g Lead
000 or LG ("triple-aught")	9.1 mm (.36")	2.2
00 ("double-aught")	8.4 mm (.33")	2.9
0 or SG("one-aught")	8.1 mm (.32")	3.1
SSG	7.9 mm (.31")	3.4
1	7.6 mm (.30")	3.8
2	6.9 mm (.27")	5.2
3	6.4 mm (.25")	6.6
4	6.1 mm (.24")	7.4

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, or shotgun shot spread. 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 large sheet of paper placed at varying distances. The hits inside 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.

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 cylindrical section of the choke diameter. Briley Manufacturing, a 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.

The choke should be tailored to the range and size of the targets. A skeet shooter, shooting at close targets might use 127 micrometres (0.005 inches) of constriction to produce a 76 cm (30 inch) diameter pattern at a distance of 19 m (21 yards). A trap shooter, shooting at distant targets might use 762 micrometres (0.030 inches) of constriction to produce a 76 cm (30 inch) diameter pattern at 37 m (40 yards). Special chokes for turkey hunting, which requires long range shots at the small head and neck of the bird, can go as high as 1500 micrometres (0.060 inches). 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

Table of shotgun chokes for a 12 gauge shotgun using lead shot
Constriction (micrometres)	Constriction (inches)	American Name	percentage of shot in a 76 cm (30 in) circle at 37 m (40 yd)	Total spread at 37 m (cm)	Total spread at 40 yds (in)	Effective range (m)	Effective range (yd)
0	.000	Cylinder	40	150	59	18	20
127	.005	Skeet	45	132	52	21	23
254	.010	Improved Cylinder	50	124	49	23	25
381	.015	Light Modified
508	.020	Modified	60	117	46	32	35
635	.025	Improved Modified
762	.030	Light Full		109	43
889	.035	Full	70			37	40
1143	.045	Extra Full
1270	.050	Super Full

Other specialized choke tubes exist as well. Some turkey hunting tubes have constrictions greater than "Super Full", or additional 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. A number of recent spreader chokes, such as the Briley "Diffusion" line, actually use rifling in the choke to spin the shot slightly, creating a wider spread. The Briley Diffusion uses a 1 in 36 cm twist, as does the FABARM Lion Paradox shotgun.

Oval chokes, which are designed to provide a shot pattern wider than it is tall, are sometimes found on combat shotguns, primarily those of the Vietnam War era. Military versions of the Ithaca 37 with duckbill choke were used in limited numbers during the Vietnam War by US Navy Seals. It arguably increased effectiveness in close range engagements against multiple targets. Two major disadvantages plagued the system. One was erratic patterning. The second was that the shot would spread too quickly providing a very limited effective zone.

Offset chokes, where the pattern is intentionally slightly off of center, 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.

 

winchester

A Winchester M1897, one of the first successful pump-action shotgun designs

In pump-action shotguns, a sliding forearm handle (the pump) works the action, extracting the spent shell and inserting a new one while cocking the hammer or striker as the pump is worked. A pump gun is typically fed from a tubular magazine underneath the barrel, which also serves as a guide for the pump. The rounds are fed in one by one through a port in the receiver, where they are lifted by a lever called the elevator and pushed forward into the chamber by the bolt. A pair of latches at the rear of the magazine holds the rounds in place and facilitates feeding of one shell at a time. If it is desired to load the gun fully, a round may be loaded through the ejection port directly into the chamber, or cycled from the magazine, which is then topped off with another round. Well-known examples include the Winchester Model 1897, Remington 870 and Mossberg 500/590.

Pump-action shotguns are common hunting, fowling and sporting shotguns. Hunting models generally have a barrel between 600–700 mm (24"-28"). Tube-fed models designed for hunting often come with a dowel rod or other stop that is inserted into the magazine and reduces the capacity of the gun to three shells (two in the magazine and one chambered) as is mandated by U.S. federal law when hunting migratory birds. They can also easily be used with an empty magazine as a single-shot weapon, by simply dropping the next round to be fired into the open ejection port after the spent round is ejected. For this reason, pump-actions are commonly used to teach novice shooters under supervision, as the trainer can load each round more quickly than with a break-action, while unlike a break-action the student can maintain his grip on the gun and concentrate on proper handling and firing of the weapon.

Pump action shotguns with shorter barrels and no barrel choke (or very little) are highly popular for use in home defense, military and law enforcement, and are commonly known as riot guns. The minimum barrel length for shotguns in most of the U.S. is 18" (457 mm), and this barrel length (sometimes 18.5"-20" (470–500 mm) to increase magazine capacity and/or ensure the gun is legal regardless of measuring differences) is the primary choice for riot shotguns. The shorter barrel makes the weapon easier to maneuver around corners and in tight spaces, though slightly longer barrels are sometimes used outdoors for a tighter spread pattern or increased accuracy of slug projectiles. Home-defense/law enforcement shotguns are usually chambered for 12-gauge shells, providing maximum shot power and the use of a variety of projectiles such as buckshot, rubber, sandbag and slug shells, but 20-gauge (common in bird-hunting shotguns) or .410 (common in youth-size shotguns) are also available in defense-type shotgun models allowing easier use by novice shooters.

A riot shotgun has many advantages over a handgun or rifle. Compared to "defense-caliber" handguns (chambered for 9mm Parabellum, .38 Special, .357 Magnum, .40 S&W, .45ACP and similar), a shotgun has far more power and damage potential (up to 10 times the muzzle energy of a .45ACP cartridge), allowing a "one-shot stop" that is more difficult to achieve with typical handgun loads. Compared to a rifle, riot shotguns are easier to maneuver due to the shorter barrel, still provide better damage potential at indoor distances (generally 3–5 meters/yards), and reduce the risk of "over penetration"; that is, the bullet or shot passing completely through the target and continuing beyond, which poses a risk to those behind the target through walls. The wide spread of the shot reduces the importance of shot placement compared to a single projectile, which increases the effectiveness of "point shooting" - rapidly aiming simply by pointing the weapon in the

 

Break-action

A view of the break-action of a typical double-barrelled shotgun, shown with the action open

Break-action

For most of the history of the shotgun, the break-action breech loading double was the most common type, typically divided into two subtypes: the traditional "side by side" shotgun features two barrels mounted one beside the other (as the name suggests), whereas the "over and under" shotgun has the two barrels mounted one on top of the other. Side by side shotguns were traditionally used for hunting and other sporting pursuits (early long barreled side-by side shotguns were known as Fowling Pieces for their use hunting ducks and other birds), whereas over and under shotguns are more commonly associated with sporting use (such as clay pigeon/skeet shooting). Both types of double-barrel shotgun are used for hunting and sporting use, with the individual configuration largely being a matter of personal preference.

Another, less commonly encountered type of break-action 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, drillings with three and even four (a vierling) shotgun barrels were made.

 

AU

A U.S. Marine fires a Benelli M4 shotgun during training in Arta, Djibouti, December 23, 2006.

The wide range of forms the shotgun can take leads to some significant differences between what is technically a shotgun and what is legally considered a shotgun. A fairly broad attempt to define a shotgun is made in the United States Code (18 USC 921), which 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."

A rifled slug, with finned rifling designed to enable the projectile to be safely fired through a choked barrel, is an example of a single projectile. Some shotguns have rifled barrels and are designed to be used with a "saboted" bullet; one which is typically encased in a two-piece plastic ring (sabot) designed to peel away after it exits the barrel, leaving the bullet, now spinning after passing through the rifled barrel, to continue toward the target. These shotguns, although they have rifled barrels, still use a shotgun-style shell instead of a rifle cartridge and may in fact still fire regular multipellet shotgun shells, but the rifling in the barrel will affect the shot pattern. The use of a rifled barrel blurs the distinction between rifle and shotgun, and in fact the early rifled shotgun barrels went by the name Paradox for just that reason. Hunting laws may differentiate between smooth barreled and rifled barreled guns.

Also, many people would likely call a fully automatic shotgun a shotgun, even though legally it would fall into a different category. Amongst the general populace, any gun that fires shotgun shells could be considered a shotgun. This might include the rare shot-pistol (a pistol designed to fire a standard shotgun shell).

Riot gun has long been a synonym for a shotgun, especially a short-barreled shotgun. During the 19th and early 20th century, these were used to disperse rioters and revolutionaries. The wide spray of the shot ensured a large group would be hit, but the light shot would ensure more wounds than fatalities. When the ground was paved, police officers would often ricochet the shot off the ground, slowing down the shot and spreading pattern even further. To this day specialized police and defensive shotguns are called riot shotguns. The introduction of rubber bullets and bean bag rounds ended the practice of using shot for the most part, but riot shotguns are still used to fire a variety of less lethal rounds for riot control.

A sawed-off shotgun (or "sawn-off") refers to a shotgun whose barrel has been shortened, leaving it more maneuverable, easier to use at short range and more readily concealed. Many countries establish a legal minimum barrel length that precludes easy concealment (this length is 18" (457 mm) in the U.S.). The sawed-off shotgun is sometimes known as a "Lupara" (in Italian a generic reference to the word "Lupo" ("Wolf")) in Southern Italy and Sicily.

Coach guns are similar to sawn-off shotguns, except they are manufactured with an 46 cm (18") barrel and are legal for civilian ownership in some jurisdictions. Coach guns are also more commonly associated with the American Old West or Australian Colonial period, and often used for hunting in bush, scrub, or marshland where a longer barrel would be unwieldy or impractical.

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 (36 inches), with some measuring up at less than 63 cm (25 inches). 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, but infrequently are available in modified choke as well. One example of a backpacker shotgun is the Verney-Carron Snake Charmer or the pistol grip Snake Charmer II.

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.