Shotguns are classified by which measurement?

• A. Gauge
• B. Caliber
• C. Barrel length
• D. Chamber size

Answer: (A)

Shotguns are categorized by gauge, a measurement of the bore diameter. Gauge is based on an old system: it defines how many lead balls of that bore would weigh one pound. Because of that relationship, a smaller gauge number means a larger bore. For example, a 12-gauge shotgun has a larger bore than a 20-gauge shotgun, which is why gauge is the standard way to classify shotguns and determine compatible ammunition.

Caliber is the term usually used for rifles and handguns, expressed in inches or millimeters. Barrel length and chamber size describe other characteristics—length affects handling and velocity, while chamber size relates to the ammunition it can fire—but they are not the primary way shotguns are categorized.