20-gauge shotgun
The 20-gauge shotgun, also known as "20-bore", is a type of smooth-bore shotgun that fires a shell that is smaller in caliber (.615 in (15.6 mm)) than a 12-gauge shotgun (.729 in (18.5 mm)). It is often used by beginning shooters for target practice and for hunting small game.
| 20 gauge | ||||||||||||||||||||||||
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 A 2¾" 20 gauge shell loaded with number 7 1/2 birdshot | ||||||||||||||||||||||||
| Type | Shotgun | |||||||||||||||||||||||
| Place of origin |  United Kingdom | |||||||||||||||||||||||
| Production history | ||||||||||||||||||||||||
| Manufacturer | Various | |||||||||||||||||||||||
| Variants | 2½" (63.5 mm), 2¾"(70 mm), 3" (76.2 mm) | |||||||||||||||||||||||
| Specifications | ||||||||||||||||||||||||
| Shoulder diameter | .673 in (17.0942mm) | |||||||||||||||||||||||
| Base diameter | .692 in (17.576mm) | |||||||||||||||||||||||
| Rim diameter | .761 in | |||||||||||||||||||||||
| Rim thickness | .050 in | |||||||||||||||||||||||
| Case length | 2.270 in | |||||||||||||||||||||||
| Primer type | Shotshell Primer | |||||||||||||||||||||||
| Maximum pressure | 12,000 psi (83 MPa) | |||||||||||||||||||||||
| Ballistic performance | ||||||||||||||||||||||||
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Description
It takes 20 lead balls of the diameter of a 20-gauge shotgun bore to equal one pound, while it only takes 12 lead balls of the diameter of a 12-gauge shotgun bore to equal the same weight. A 20-gauge shotgun is more suitable for hunting certain types of game or for some hunters because it recoils less, and the guns weigh less and may be smaller.
Specifications
20-gauge shotguns are especially suitable for hunting game birds such as quail, grouse, turkey, and other game when using shot shells. A 20-gauge can also shoot slugs and buckshot and thereby become an effective deer-hunting gun. While shotguns loaded with slugs are usually less accurate than rifles, they often have better stopping power at short range, although this depends on the amount of propellant in the shell's load.
Performance
In addition, 20-gauge shotguns have less recoil than 10-, 12-, or 16-gauge versions on average, and may be more desirable to those who want to experience less recoil for prolonged shooting. The lower recoil also makes a 20-gauge appropriate for younger (or conversely, middle-aged or elderly) shooters who may have a difficult time firing a larger shotgun. However, recoil is also dependent on the weight of the gun itself; for instance, a 4.5 lb (2.0 kg) 20-gauge can have more recoil than an 8 lb (3.6 kg) 12-gauge. This is widely considered a flaw in the design of so-called 'youth' guns.