What does the term "gauge" refer to in shotguns?

The term "gauge" in shotguns refers specifically to the bore diameter of the shotgun. It indicates the size of the shotgun's interior barrel and is a measurement of how many lead balls of the diameter equal to the bore can be made from one pound of lead. For example, a 12-gauge shotgun means that 12 balls of lead, each with a diameter equal to the barrel's diameter, weigh one pound.

Understanding gauge is crucial for proper shotgun selection, as it dictates the type of ammunition that can be safely and effectively used. Different gauges will shoot different-sized shells, and using the incorrect size can lead to safety issues or suboptimal performance when hunting or shooting. The other options — the length of the shotgun barrel, the weight of the shotgun, and the type of ammunition used — do not directly relate to the term "gauge," which specifically denotes the diameter of the shotgun's bore.