The 20-gauge shotgun, also known as 20 bore, is a type of smoothbore shotgun. 20-gauge shotguns have a bore diameter of .615 in, while the 12-gauge has a bore diameter of .729 in. 12-gauge and 20-gauge shotguns are the most popular gauges in the United States. The 20-gauge is popular among upland game hunters, target shooters, and skeet shooters.

Description

20 lead balls of the diameter of a 20-gauge shotgun bore weigh one pound, while just 12 lead balls of the diameter of a 12-gauge shotgun bore equals the same weight. A 20-gauge shotgun is more suitable for hunting certain types of game or for some hunters because it may have less felt recoil than an identical shotgun in a larger gauge, and guns may be smaller and weigh less, though this has changed since the introduction of the 3-inch magnum shotshell. Regarding the yellow body tube color that 20-gauge ammunition usually has, it has been reserved in SAAMI documentation saying "SAAMI has reserved yellow for 20 gauge ammunition" "This ammunition shall have a body tube that is primarily yellow" "Yellow shall not be used for any other gauge/bore shotshell body" "No other recommendations are made as to the color of service body tubes for other gauges/bores" This color designation may be designed to aid in identifying 20-gauge shells. A 20 ga shell if mixed in with 12 ga. shells will enter the chamber and lodge inside the bore at the end of the chamber. If a 12 ga shell is loaded and fired behind the lodged 20 ga shell the result is catastrophic.

Specifications

20-gauge shotguns are especially suitable for hunting game birds such as quail, grouse and mallards when using lead-free birdshot. A 20-gauge buckshot load would most commonly be utilized in close- to mid-range self-defense scenarios. While slug loads are ballistically less accurate than rounds used in rifles, powerful, high-grain slug loads can provide improved ballistics for hunting deer when paired with a rifled barrel.

Recoil

While the 20-gauge is generally perceived to have less felt recoil than the 12-gauge, there are too many variables, including gun weight, type of shotgun, stock pattern, shot weight, shell size, etc. for that opinion to be a fact. There may be little to no difference between the two when using target ammunition. Loads for waterfowl will tend to produce more felt recoil in a 12-gauge shotgun than in a 20, but this may not be the case depending on the gun used. Full-power 20-gauge shells fired from a light 5 lb gun will have more felt recoil than those fired from a heavy 7 lb gun. To do a true comparison, two identical shotguns, one in 12 and one in 20, with identical ammunition (other than gauge) have to be compared. In those cases, the 12-gauge does generate more recoil energy than the 20.