by cartridge was lengthened by about to fit the sharp-fronted steel bolt. Another cartridge version was designed that contained a miniature rocket, which when fired makes a visible streak in the water. Next, Vladimir Simonov designed the rifle. The objective was ambitious; nobody had ever before tried to build a functioning automatic underwater firearm. The most important problem was designing a receiver that could work under water. Water is essentially incompressible, so the structure had to let water move around easily; as a result, its receiver is open at the rear. Since it operates on the principle of gas discharge, it has a gas controller to let it work both underwater and on land. The APS was adopted in the mid-1970s. Afterwards, there was lengthy improvement work on the APS. One improvement was fitting a perforated gas pipe with a special shield to break up the emitted gas bubbles, making targeting easier and reducing the visibility of the bubbles, allowing stealthier firing of the weapon. The APS was the primary weapon of Soviet frogmen and Serbian river flotilla frogmen. However, since the conception of this new weapon there were objections. It was the perfect weapon for the Soviet frogmen's underwater operations, but it was less useful for Spetsnaz soldiers fighting both on land and underwater. The APS can operate on land, but its effective range does not exceed 50 metres, and the rifle's lifetime drops to 180 shots in air from 2,000 shots underwater. Therefore, they mostly carried a SPP-1 pistol for self-defence under water and an AK-74 to fight on land. At the end of the 1980s the ASM-DT amphibious rifle was developed. Users : Used by MARCOS commandos. : by the 82nd River Underwater Demolition Company of the 72nd Brigade for Special Operations See also Bibliography Piotr Taras „Strzałki” dla płetwonurków, Komandos 9/93. Zbigniew Gwóźdź, Strzały pod wodą, Komandos 7/8/96. Leszek Erenfeicht, Rosyjska broń strzelecka dla płetwonurków, Strzał 5/2003. Wiktor Suworow, Specnaz. Historia sił specjalnych Armii Radzieckiej, Wydawnictwo Adamski i Bieliński, Warszawa 1999. References External links A real APS used in filming game footage for the Call of Duty: Ghosts videogame. Assault rifles of the Soviet Union Soviet inventions Cold War firearms of the Soviet Union Underwater rifles Tula Arms Plant products Flechette firearms Military equipment introduced in the 1970s