This compact weapon system based on the AKSB 74U shortened assault rifle and adopted for service with special operations units of the Soviet Army an the early 1980s, combines not only two types of projectiles (bullet and grenade) but also two basic principles of shot noise reduction through powder gases expansion and their cutoff in the chamber.
Earlier, in 1970s, special operations units of the Soviet Army adopted for service the Tishina special silenced assault rifle/grenade launcher system; it included a "noiseless" modification of the 7.62mm AKMS Kalashnikov assault rifle (with the PBS-1 sound/flash suppressor) and a special 30 mm silenced under barrel grenade launcher. However, with the new small arms system using the 5.45mm low-recoil intermediate cartridge entering into service in the mid-1970s, a corresponding requirement for upgrading of the silenced assault rifle/grenade launcher system was also issued. The system retained the same concept based on using the 5.45 mm AKSB 74IJ shortened assault rifle and 30 mm BS-1/BS-1M silenced underbarrel grenade launcher.
The special assault rifle/grenade launcher system was named «Kanareika» (index 6S1). The assault rifle is the AKSB 74U (index 6P27) model upgraded for mounting the 30 mm grenade launcher. The PBS-4 silent (noiseless) and fleshless firing device as mounted on the assault rifle muzzle.
The grenade launcher using a gas cutoff scheme is attached to the lower part of the forearm and rifle barrel on special attachment points. Which means that in contrast to conventional underslung grenade launchers (GP-25/GP-30) the noiseless grenade launcher cannot be attached to any standard assault rifle. The grenade launcher fires a 30 mm grenade with shaped charge warhead capable of penetrating about 10 mm thick steel sheet. Because of the specific design of the grenade launcher (a gas-operated cutoff weapon), the grenade has no propellant charge of its own. It is loaded onto the launcher barrel from the muzzle end and pushed out with a piston driven by a special blank propelling cartridge chambered from the breech end (i. e. the grenade launcher has separate loading, both from the muzzle end and from the breech end). The hollow-charge grenade can pierce up to 15 mm thick steel armour plates (up to 10 mm by the Tishina system), while retaining the required beyond-armour effect. The grenade launcher was designed primarily to destroy such targets as fuel reservoirs, parked aircraft, electronic equipment vans, tactical missile launchers, etc. Therefore, the main beyond-armour effect of the grenade is incendiary one. The loaded grenade is retained in the barrel wall by spring-action bends, hired grenade is stabilized in flight by rotation: there are three ready-made lugs on the grenade body which enter into three twist rifling’s in the barrel bore at loading.
Components and ammunition of Kanareaka assault rifle/grenade launcher system: 1 - PBS-4; 2 - 5.45x39 cartridge (7U1); 3 - AKSB 74U assault rifle with magazine; 4 - BS-1 grenade launcher; 5 - grenade for BS-1 grenade launcher; 6 - grenade propelling cartridge; 7 - magazine with grenade propelling rounds
Grenade propelling rounds are loaded into a magazine inserted in the grenade launchers pistol grip: the rounds are chambered from the breech end by a longitudinally sliding rotating rifle-type boll. The grenade launcher has a firing mechanism with a trigger and a non-automatic safety lock.
In contrast to cases of standard blank rounds intended for assault rifles the grenade propelling cartridge case Is not elongated. Its cartridge case neck is swedged inward in a star-like pattern, as it is done in conventional blank rounds. When shot is fired, powder gases of the grenade propelling cartridge press on the piston, the latter ejects the grenade out of the barrel bore and locks away (cuts off) powder gases in the chamber, thus ensuring silent and fleshless shot. Sighting range of the Kanareika grenade launcher system has been increased by 300 to 400 m compared with the Tishina system
A flip-up rack sight of the grenade launcher is mounted on the rear sight base of the assault rifle and its sighting point should be aligned with standard front sight of the assault rifle when aiming. The sight of the assault rifle proper is designed for firing rounds with the US subsonic muzzle velocity bullet.
To reduce the grenade launcher recoil kick, a recoil-absorbing pad is put on the butt plate.