ammunition boxes (at right angles to the gun carriage) and by muzzle flash suppressors. In another similarity to the ZPU series, single-barrel and four-barrel versions of the ZU-23 were also developed. However, these versions never entered service. The ZU-23-2 can be towed by a number of different vehicles. In USSR and later Russia the most frequently used towing vehicles for it were GAZ-66 4x4 trucks and GAZ-69 4x4 light trucks. The weapon is known in the Finnish forces colloquially as Sergei. Ammunition The 23 mm AA gun utilizes the same 23x152B case as the wartime VYa aircraft autocannon. Due to different loadings and primers the ammunition is not interchangeable, however: ammunition of the anti-aircraft cannon can be identified from its steel casings, ammunition for the aircraft cannon having brass cases instead. The following table lists the main characteristics of some of the available 23x152B ammunition used in 23 mm AA guns: Not only the gun itself but also the ammunition is produced in several countries. In Bulgaria, the company ARCUS Co. produces rounds and fuses for the 2A7 and 2A14 guns. Service history The ZU-23-2 first entered service with the Soviet Army in 1960. The gun is often mounted on trucks for use in both anti-aircraft and direct fire support roles. It can also be mounted on the roof of the MT-LB multi-purpose tracked APCs. A specially modified three-legged ZU-23-2 autocannon is used as the base for the BTR-DG airborne SPAAG. Cheap, easy to operate and still effective, the ZU-23-2 is still used by the Russian Army and by more than 20 other armies. From 1965 onwards, the Soviet Union began supplying the Democratic Republic of Vietnam with large shipments of weapons. The 23 mm ZU-23-2 was, along with the 37 mm M1939, the most frequently encountered anti-aircraft gun in Vietnam. Given that 83% of the USAF losses came from ground fire, the ZU-23 was probably responsible for shooting down hundreds of aircraft. During the Soviet–Afghan War, the Soviet forces placed ZU-23-2 sets in the occupied areas to secure their positions, employing them in both the static defense and direct fire support roles. In the later Afghan Civil War, the main belligerents, the Taliban and the Northern Alliance forces also employed ZU-23-2 autocannons mounted on BMP-1 and BTR-70 APCs or GAZ-66 and ZIL-131 trucks, along with SA-7 Grail or Stinger Missiles, as their primary air-defense and direct fire support weapons.