2.2 CAL FIELD CODES FOR SHOTGUNS
The gauge system of bore measurement is unique and totally different from the English caliber or metric methods of measurement. Shotgun gauges are normally expressed as whole numbers, followed by the word "gauge" or an abbreviation for it, for example 12-gauge or 12-ga. Under the English system of shotgun gauges, the lower the numerical value, the larger the bore diameter. With most common shotgun cartridge types, the bore diameter when expressed in decimals of an inch or millimeters is not the same as the gauge. A 12- gauge's bore diameter is not .12 caliber; nor is it 12 millimeters. The exception is the 410- gauge; it is a true .41-caliber bore diameter. There are also metric designations in use (listed below), but these will usually be designated in millimeters or with the abbreviation "mm." The appropriate gauge should be entered in the CAL Field. Some shotgun gauges are numerically the same as some calibers, especially metric designations. The weapon type should be designated in the Type (TYP) Field to eliminate any confusion.
Shotgun Gauges 4
22 caliber smoothbore
32 or 14 mm