The 30 mm Caliber is a standard size of heavy machine gun (specifically autocannon) ammunition used by NATO forces. The round itself has a length in the range of 8 to 12 inches (200 to 305 mm) while the projectile is ranges from 4 to 6 inches (100 to 150 mm).
Unlike its cousin the 25 mm round, the 30 mm is not typically an anti-personnel round. Instead, the 30 mm round is generally either an anti-material or anti-armor round. It is capable of taking out targets ranging from armored vehicles and Main Battle Tanks to fortified bunkers.
The U. S. Military uses 30 mm weapons in their A-10 Thunderbolt II, AH-64 Apache, LAV-25, AAAV, and as a standard ship-based munition in the upcoming Mark 46AmericanHughes M230
30 mm ammunition generally comes in three varieties: Armor Piercing, High explosive, and Training rounds. Armor Piercing and High Explosive cartridges usually also possess incendiary characteristics.