The above cartridge names are the various ways cartridges have been identified. 30-30 uses an older style for identifying cartridges. It means the projectile is .30-inches in diameter and holds 30 grains of powder. .308 and other cartridges that use similar naming conventions simply state the diameter of the bullet in inches without giving case capacity or length. .308 would be a .308-inch diameter bullet. Finally, 7.62x39 and other cartridges with similar naming functions have a bullet that is 7.62 millimeters in diameter, and the case is 39 millimeters long.