How are different types of shotguns and their ammunition identified?

Shotguns and their ammunition are identified primarily by gauge, which refers to the diameter of the bore. The gauge indicates the size of the shotgun and is derived from the number of lead balls the same diameter as the bore that would weigh one pound. For instance, a 12-gauge shotgun means that twelve lead balls of that bore diameter weigh one pound. This standardization is crucial as it determines the compatibility of the shotgun with specific ammunition types.

While the weight of the shotgun, color of the shotshell, and length of the barrel may provide some information about the shotgun's construction and capabilities, they are not standardized identifiers in the same way that gauge is. The gauge directly impacts what ammunition a shotgun can safely and effectively use, making it the essential factor for identification in this context.