The ZU-23-2, also known as ZU-23, is a Soviet towed 23×152 mm anti-aircraft twin-barreled autocannon. ZU stands for Zenitnaya Ustanovka (Russian: Зенитная Установка) – anti-aircraft mount. The GRAU index is 2A13. Development history The ZU-23-2 was developed in the late 1950s. It was designed to engage low-flying targets at a range of 2.5 km as well as armoured vehicles at a range of two kilometres and for direct defence of troops and strategic locations against air assault usually conducted by helicopters and low-flying airplanes. In 1955, KBP presented the single-barrel ZU-1 and the twin-barrel ZU-14. While the former was eventually dropped, the ZU-14 was selected and, after some modifications, entered series production. In the Soviet Union, some 140,000 units were produced. The ZU-23 has also been produced under licence by Bulgaria, Poland, Egypt and the People's Republic of China. Development of this weapon into a self-propelled anti-aircraft gun led to the ZSU-23-4 Shilka. Description The ZU-23-2 (2A13) mounts two 23 mm autocannons on a small trailer which can be converted into a stationary mount for firing the guns. While in this position the wheels are moved aside. The autocannon can be prepared for firing from the march position in 30 seconds and in emergency can be fired from the traveling position. The weapon is aimed and fired manually, with the help of the ZAP-23 optical-mechanical sight which uses manually entered target data to provide limited automatic aiming. It also has a straight-tube telescope T-3 for use against ground targets such as infantry as well as unarmored or lightly armoured vehicles. The ammo is fed by a conveyor belt from two ammunition boxes. Each of the ammunition boxes is located on the side of the twin autocannon and each carries 50 rounds. The fumes created by firing the weapon are partially removed through the side openings in the barrels. Normally, once each barrel has fired 100 rounds it becomes too hot and is therefore replaced with a spare barrel. Each weapon is normally provided with two replacement barrels as part of its standard equipment. Tulamashzavod Joint Stock Company is offering to upgrade the 2A14 guns to the 2A14M standard with a barrel life of 10,000 rounds instead of 8,000 rounds. The cannon carriage is based on the earlier ZPU-2 anti-aircraft twin heavy machine gun, which mounted two KPV 14.5×114mm heavy machine guns. ZU-23-2 can be identified by different placement of the