What is the difference between an 8 gauge and a 12 gauge shotgun?
The caliber of shotguns is measured in terms of gauge (U.S.) or bore (U.K.). The gauge number is determined by the number of solid spheres of a diameter equal to the inside diameter of the barrel that could be made from a pound of lead. 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 (= 36), 32, 28, 24, 16, and 10 (19.7 mm) gauge and 9 mm (.355 in.) and .22 (5.5mm) rimfire calibres have also been produced (although 10, 12, 16, 20, 28, .410, and .22 are the only legal hunting gauges/calibers in most U.S. states). To further complicate matters, typical handgun chamberings such as 9 mm Parabellum, .45 ACP, .38 Special/.357 Magnum, .44 Special/.44 Magnum, and .45 Colt and others bearing a “shot” load have been brought to market by CCI/Speer–either crimped in or in a plastic casing replacing the bullet.
