Military ammunition is used for a wide variety of weapons systems and platforms, from infantry-borne small arms to artillery and tank guns and fighter aircraft. While ammunition is sometimes designed only to serve a specific weapons system, international standards do exist that allow some ammunition to be interoperable among different platforms, for example the NATO 5.56x45mm rifle cartridge.
Ammunition usually has one of two effects on a target – either the projectile within the round acts purely kinetically, or it may deliver explosives that detonate to provide increased damage. In addition to the projectile itself, rounds of ammunition typically contain a propellant, which burns to provide the kinetic energy that propels the projectile.
Explosive ammunition such as artillery and tank gun shells also typically requires a fuse, which is used to detonate the explosives. Fuses may be adjustable to enable different detonation modes such as point of impact, time delays, or proximity.
Weapons platforms may be able to utilize multiple types of ammunition. For instance, in addition to regular ammunition, rifles may be able to fire short-range or tracer rounds, as well as be fitted with dummy or blank rounds for training purposes.
Ammunition caliber refers to the internal diameter of the barrel of the weapon that the round is designed for, and may be measured in inches or millimeters. While size classification systems may vary, small-bore calibers typically refer to .32 inches or less, medium-bore calibers to between .33 and .39 inches, and large-bore calibers to rounds over .40 inches.
Ammunition may be stored and carried in a variety of ways. Small-arms ammunition for infantry rifles and machine guns is usually delivered to the weapon in box magazines or bandoliers, and numbers of these as well as single rounds may be stored in rugged metal containers. Before distribution, ammunition may be stored at an ammunition dump at a military facility. Temporary storage areas such as at forward operating bases or on board warships may also be referred to as magazines.