A measure of the size of a bullet. It corresponds to the largest diameter of its cross-section and is commonly measured in inches or millimeters. The metric version also has a measure for the length of the case for additional information on the power of a cartridge, e.g. 8X57mm means a bullet width of 8mm and a case length of 57mm. The greater the case length, the greater the power. Common calibers in discussions of gun violence include the following. Handgun: 9x19mm (the most widespread handgun cartridge in the world), .40, .45. Rifle: .223, 5.56X45mm; .308, 7.62X51mm.
