1.59-inch breech-loading Vickers Q.F. gun, Mk II

The 1.59-inch breech-loading Vickers Q.F. gun, Mk II was a British light artillery piece designed during World War I. Originally intended for use in trench warfare, it was instead tested for air-to-air and air-to-ground use by aircraft. Although it fired shells and had no capability to launch rockets, it was widely but misleadingly known as the "Vickers-Crayford rocket gun." Vickers designed the gun early in World War I, intending it as a piece of light artillery for use by infantry in trenches attacking machine gun positions and pillboxes. To make it portable for infantry use, it was very small and light for a gun of its calibre. Its light construction dictated a low muzzle velocity, which resulted in it having a short range. It was too light to withstand the detonation of standard British explosive propellants, so its ammunition used ballistite packed in cambric bags instead. The gun fired a 1.2-pound (0.54 kg) high-explosive shell at 800 feet (244 meters) per second; it also could fire an armour-piercing round at 1,000 feet (305 meters) per second. The guns 40x79R cartridge was a shortened version of the naval 40x158R anti-aircraft cartridge, with the shell case reduced from 158 mm (6.22 inches) to 79 mm (3.11 inches) in length. The gun was, for ease of use in trenches, single shot; the gunner had to extract the empty case of a fired cartridge manually and reload the gun after firing each round, which gave it a low rate of fire. It had a simple block breech with percussion gear, and was mounted on a non-recoiling frame consisting of a hydraulic buffer, trunnion block, and rear guide tube. Hand grips were mounted on the guide tube. The gun had a large muzzle brake to reduce recoil. Vickers manufactured the gun at its plant in Crayford, England. The concept of using the 1.59-inch breech-loading Vickers Q.F. gun, Mk II in the trenches was superseded by that of the trench mortar, which was simpler, cheaper, easily portable, and more effective.