APS underwater rifle The APS underwater assault rifle ( APS stands for Avtomat Podvodny Spetsialny ( Автомат Подводный Специальный ) or " Special Underwater Assault Rifle " ) is an underwater firearm designed by the Soviet Union in the early 1970s . It was adopted in 1975 . Made by the Tula Arms Plant ( Тульский Оружейный Завод , Tulsky Oruzheiny Zavod ) in Russia , it is exported by Rosoboronexport . Underwater , ordinary - shaped bullets are inaccurate and very short - range . The APS fires a steel bolt caliber 5 . 66 mm ( specially designed for this rifle and is often mistaken as 5 . 56 mm ) and 120 mm ( 4 . 75 in ) long . Its magazine holds 26 cartridges . The APS ' s barrel is not rifled ; the fired projectile is kept in line by hydrodynamic effects . As a result , the APS is somewhat inaccurate when fired out of water . The APS has a longer range and more penetrating power than speargun s . This is useful in such situations as shooting through reinforced dry suit s , and protective helmet s ( whether air - holding or not ) , thick tough parts of breathing sets and their harness es , and plastic casings and transparent covers of some small underwater vehicles . The APS is more powerful than a pistol , but is bulkier and takes longer to aim , particularly swinging its long barrel and big flat magazine sideways through water . History . The rising threat of attacks by frogmen in naval bases caused various anti - frogman techniques to be developed , and in the USSR one of these was guard frogmen sent to stop the attackers . At first these guard frogmen were armed only with knives and AK - type rifles . The AK - 47 was carried in a waterproof case and could only be used on the surface , so the only effective underwater weapon against enemy frogmen was the knife . The SPP - 1 underwater pistol was accepted in 1971 , but soon proved to be useful only in close - up self - defence , not in attacking more distant targets . Vladimir Simonov undertook the job of developing an underwater assault rifle . To allow the rifle ' s mechanism to work underwater , there had to be room for the flow of the water pushed aside by moving parts and by the gas produced by the propellant explosive in the cartridge . The APS rifle was accepted for use in the mid - 1970s . One special improvement was a perforated gas tube , and in the sighting . Its design engineer received a state award in 1983 . As with the SPP - 1 the first stage of the work was to develop a cartridge . A 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 ever before tried to build a functioning automatic underwater firearm . The most important problem was designing a receiver that could work under water . Compared to air , water is relatively 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 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 . 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 use for Spetznaz soldiers fighting both on land and under water . Out of water the APS can shoot , but its effective range does not exceed 50 meters , and the rifle ' s lifetime drops to 180 shots in air from 2000 shots underwater . Therefore they mostly carried a SPP - 1 pistol for self - defense under water and an AK - 74 to fight on land . Therefore , at the end of the 1980s the ASM - DT amphibious rifle was developed .