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.