Editing Shotgun (section)

=== Gauge ===<!-- Other articles link here -->
[[File:Shotgun.jpg|thumb|right|A [[United States Army]] soldier armed with a [[Mossberg 500]] shotgun]]
{{Main|Gauge (firearms)}}
The gauge number is 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. Each gauge has a set [[caliber]]. By far the most common gauges are 12 (0.729 in, 18.5mm diameter) and 20 (0.614 in, 15.6mm), this includes other more or less common gauges, such as the 10, 16, 24, 28, 32, and 67 ([[.410 bore]]) gauge.

Different gauges have different typical applications. 12-gauge shotguns are common for hunting geese, large ducks, or other big larger gamebirds; professional skeet and trap shooting; military applications; and home-defense applications. 16-gauge shotguns were once common for hunters who wanted to use only a single shotgun for gamebirds normally pursued with 12 or 20-gauge shotguns, but have become rarer in recent years. 20-gauge shotguns are often used for gamebirds such as doves, smaller ducks, and quail. 28-gauge shotguns are not as common, but are classic quail-hunting guns. .410 gauge shotguns are typically used for squirrel hunting or for sportsmen seeking the challenge of killing game with a smaller load.

Other, less common shotgun cartridges have their own unique uses. Ammunition manufacturer CCI produces 9mm Parabellum (.355 in.) and several other popular pistol calibers up to .45 ACP (11.43mm), as well as smaller calibers such as .22 Long Rifle (5.5mm) and .22 Magnum (5.5mm). These are commonly called snake shot cartridges.<ref>{{cite book|author=Hearst Magazines|title=Popular Mechanics|url=https://books.google.com/books?id=0N4DAAAAMBAJ&pg=PA197|date=October 1947|publisher=Hearst Magazines|page=197}}</ref> Larger gauges, up to 4 bore, too powerful to shoulder, have been built, but were generally affixed to small boats and referred to as [[punt gun]]s. These were used for commercial [[Anatidae|waterfowl]] hunting, to kill large numbers of birds resting on the water.

[[File:Bond Arms Texas Defender Cowboy .45 .410.JPG|thumb|Bond Arms Cowboy Defender .45 Colt/.410 Shotshell Derringer]]
Handguns 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". [[Derringer]]s such as the "[[Bond Arms|Snake Slayer and Cowboy Defender]]" are popular among some outdoors-men in the South and Southwest regions of the United States. There are also some revolvers, such as the [[Taurus Judge]] and [[Smith & Wesson Governor]], that are capable of shooting the [[.45LC]]/.410 rounds; but as with derringers they are not considered shotguns.

The [[.410 bore]] (10.4&nbsp;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 beginner's 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.<ref>{{cite web|url=http://www.chuckhawks.com/410bore.htm |title=410 Gauge |publisher=Chuckhawks.com |access-date=19 February 2015}}</ref> 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 shotgun|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 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.