The GP-30 Obuvka, GP-25 Kastyor and BG-15 Mukha are under barrel grenade launchers for the AK-series of assault rifle. They were first seen by the west in 1984 during the Soviet Invasion of Afghanistan. The initial version was designated BG-15, and was fitted under the barrel of AK-74 assault rifles. The main production version, the GP-25 has a different sighting system. The latest version the GP-30 is an evolved version of the GP-25, being lighter, easier to make, and easier to use.
The grenade launchers are similar in appearance and fire the same 40 mm ammunition.
The GP-30 is a stripped-down model grenade launcher, consisting of a very short rifled 40 mm barrel in front of a basic trigger mechanism with minimal hand grip. On top of the barrel is mounting gear to attach the weapon under the barrel of an AK-series assault rifle, where it is designed to be fired from.
A grenade is first muzzle loaded into the barrel, the weapon is aimed, then the self cocking trigger is pulled to fire the weapon. This fires the percussion cap at the base of the grenade which triggers the nitrocellulose propellant inside the body of the grenade. The hot expanding gas from the propellant is forced through vents in the base of the grenade that move grenade along the barrel, and at the same time force the driving band to engage with the twelve rifling grooves. The rifling imparts stabilizing spin to the projectile.
The barrel has a life of about 400 rounds.