mm (6.1 in) is a NATO-standard artillery shell caliber that is used in many field guns, howitzers, and gun-howitzers. It is defined in AOP-29 part 1 with
name means that it had a bore diameter of 1.1 in (28mm) and barrel caliber of 75 (1.1inches × 75 = 82.5 in (2.1 m)). The gun was designed to replace the
Italian anti-aircraft gun QF 3.7-inch AA gun: contemporary British anti-aircraft gun, firing a 28 pounds (13 kg) shell 85 mm air defense gun M1939 (52-K):
United States naval gun terminology indicates the gun fired a projectile 5 inches (127 mm) in diameter, and the barrel was 38 calibers long. The increased