Twelve- and 20-gauge shotguns are popular choices among hunters and sport shooters alike. Both gauges are effective at hunting birds and small game, and both feature prominently in competitions such as trap shooting and sporting clays. The guns also come in a variety of models, such as single-barrel, side-by-side double barrel, and over-and-under double barrel.
The larger of the two gauges, the 12-gauge shotgun features a wider bore diameter of .729 inches. Hunters and sport shooters often choose this gauge for its effectiveness in bird and skeet shooting, because its range is typically longer than that of the 20-gauge. Because of its heavier weight, the 12-gauge can generate a larger recoil, or kick to the shoulder, particularly with big shells.
The 20-gauge shotgun features a smaller bore diameter of .615 inches. Also a preferred shotgun for bird and sport shooters, it generally sells for less than a 12-gauge and is an adequate gun for the beginner. The 20-gauge's lighter weight makes it a popular choice among hunters who cover a lot of ground, and its recoil is minimal to nonexistent.
The standard shot load for a 12-gauge shotgun is 1-1/8 ounces. Heavier load sizes of 1-1/4 ounces are effective for longer ranges and more difficult targets. The shorter shot column of a 12-gauge shell offers a ballistic advantage because fewer pieces of shot are deformed by friction as they travel through the barrel.
The standard shot load for a 20-gauge shotgun is 7/8 ounces, although heavier loads are also available. Load sizes ranging from 1 ounce to 1-1/4 ounces work for longer ranges, though the 20-gauge's range is shorter than that of the 12-gauge.
Both the 12-gauge and 20-gauge come in a variety of actions. Single-shot actions open at the bottom of the barrel, and you must load the shell manually. A bolt action takes only one shell in the chamber; you load the shell manually by sliding a bolt back and forth in the barrel. With a pump-action gun, you usually can load three shells, pumping each into the barrel manually after the last is shot. Like the single-shot, a double-barrel action opens at the bottom of the barrel, where you manually load two shells. Finally, a semi-automatic shotgun can load up to five shells; each shell loads automatically into the barrel after the last is shot.