Afanasev A - 12 . 7 The Afanasev A - 12 . 7 is a heavy machine gun developed by Nikolay M . Afanasev in 1949 and adopted for service in 1953 . This gun was supposed to have a considerably higher rate of fire than its predecessor — the Berezin UB aircraft machine gun . Due excessive barrel wear however , it was eventually limited by an electrical trigger to a rate comparable to the Berezin UB . Initially intended to be mounted in the defensive turret s of the Tu - 4 bomber , the A - 12 . 7 was ultimately installed only in trainer aircraft and helicopters . Nevertheless , it was produced for 30 years . History . After the Second World War various attempts were made to increase the rate of fire of the Berezin machine gun . Reducing the cycle time by increasing the speed of the moving parts was the most obvious thing to do . However , this resulted in a considerable reduction of life and reliability . Another attempt was to reduce the motion length of the moving parts while retaining their speed within permissible limits . N . M . Afanasev took a different approach by introducing an acceleration lever , which transferred the energy of a short motion actuating slide into a long motion of a chamber ing and case extraction arm . This way the motion length of the actuating slide could remain shorter than the overall length of the cartridge , thus increasing the rate of fire . Later , the same operating mechanism was used in the 23mm AM - 23 and ZSU - 23 cannon as well . Afanasev ' s prototype 12 . 7mm machine gun was designated TKB - 481 and reached an impressive rate of fire of 1 , 400 rounds per minute . However , because of barrel wear problems a special electrical trigger system was introduced , that artificially reduced the rate of fire to 800 - 1 , 100 rounds per minute . With this modification the barrel life increased to 4 , 000 rounds , however the gun no longer had any distinct advantages over the Berezin UB . Nevertheless , in the autumn of 1953 , Afanasev ' s 12 . 7mm aircraft machine gun was adopted put into production under the designation A - 12 . 7 . The GRAU index of the weapon is 9 - A - 016P . The A - 12 . 7 machine gun is a gas - operated weapon with a vertically moving wedge breechblock . On the actuating slide two pivoting , jointed chambering levers are mounted . Those chambering levers actually work like the arms of a praying mantis . The upper , longer lever is used to ram the cartridge from the belt link into the chamber . An extraction claw on its forward end is used to extract the fired cartridge case . The lower lever protrudes into the weapon housing and has a U - shape d recess on its lower end . As the actuating slide moves back and forth , a traverse lug in the weapon housing is cammed into this recess to guide the chambering levers . The A - 12 . 7 aircraft machine gun has an electrical sear mechanism that is operated by a voltage of 26V . At the back plate a spring buffer is located . Ammunition may be fed from either the left or from the right side . A pneumatically operated charging mechanism on the left side of the receiver is used to charge the machine gun and to clear misfires . The cylindrical housing on the right side of the receiver contains the return spring of the actuating slide . The internal machining of the barrel of the A - 12 . 7 was the same as the one of the DShK heavy machine gun , with 8 grooves 0 . 17 mm deep and 2 . 8 mm wide . The A - 12 . 7 machine gun never armed the Tu - 4 bomber as initially intended . By then , machine guns were considered obsolescent for this purpose and 23mm cannon were employed instead . Therefore the A - 12 . 7 was only used in training aircraft and helicopter s . The UTI trainer versions of the MiG - 15 , MiG - 17 and MiG - 19 aircraft carried a single A - 12 . 7 machine gun . The main application of Afanasev ' s 12 . 7mm machine gun , however , was the armament of helicopters . The Mi - 4A helicopter was equipped with a single gun with 200 rounds in the gondola below the fuselage . A single A - 12 . 7 was also installed in the nose of the Mi - 6A transport helicopter . The Mi - 8TV had an A - 12 . 7 machine gun in its nose as well and on the Mi - 24A it was installed in the turret NUV - 1 . An exemplar can be seen at the and another at Aviation Museum of Central Finland .