GP-25 Kostyor

The GP-25 Kostyor ("Bonfire") is a Russian 40 mm muzzle-loaded under-barrel grenade launcher for the Kalashnikov family, the head of a group that also includes the GP-30 Obuvka ("Shoe") and the GP-34. GP stands for Granatomyot Podstvolnyj, "under-barrel grenade launcher". Development started in 1966 at the Central Design and Research Bureau of Sporting and Hunting Arms (TsKIB SOO) for the AKM, continued through the 1970s, and the weapon was accepted into Soviet service in 1978. The main production GP-25 fits the AKM and AK-74; the GP-30, in service from 1989, is lighter with the sight moved to the right and is intended for the AK-100 series; the GP-30M is a simplified model with a shorter barrel and minimal grip. The current Izhmash GP-34 further redesigns the right-side sight, fits Kalashnikov rifles directly without adaptors or removing the handguard, and adds a firing-pin safety lever plus a mechanism preventing a loaded round from shifting or falling out when the muzzle points down.

The launcher clamps to the underside of the rifle barrel and is loaded from the muzzle. Pulling the double-action trigger fires a percussion cap in the base of the grenade, igniting nitrocellulose propellant inside the grenade body; the expanding gas escapes through openings in the base to drive the projectile up the barrel while forcing its driving band into the twelve grooves of the rifling, which imparts stabilising spin. Rate of fire is 5 to 6 aimed rounds per minute or 20 for area suppression, and the barrel has a service life of about 400 rounds.

The ammunition design is the key difference from Western practice. Russian 40 mm VOG-25 rounds are a single caseless piece with propellant and primer contained in the base of the grenade, rather than the two-piece case-and-projectile arrangement of the 40x46mm rounds used in breech-loading launchers such as the M203; nothing remains in the barrel after firing, so the next grenade can be loaded immediately. The two families are not interchangeable. The VOG-25 high-explosive fragmentation round has a six-metre lethal radius, a total range of 400 m and an effective range of 150 m. The VOG-25P is a bounding version whose nose charge throws it 50 cm to 1.5 m into the air before a delay fuse detonates it, with the same lethal radius. Newer VOG-M and VOG-PM rounds claim at least 1.5 times the effectiveness. Smoke grenades are issued in GRD-50, GRD-100 and GRD-200 forms for use at 50, 100 and 200 m, each producing a 20 cubic metre cloud lasting a minute in winds up to 5 m/s, and a Gvozd ("Nail") tear gas grenade is also available.

The family is in service with the Russian Armed Forces and across the former Soviet sphere and its export customers, including Algeria, Angola, Armenia, Botswana, Burundi, the Democratic Republic of the Congo, Cyprus, Greece, India, Iran's IRGC, Lithuania, North Korea, North Macedonia, Pakistan, Syria, Ukraine and Vietnam. Bulgaria's Arsenal AD builds it under licence as the UBGL and UBGL-1, Serbia's Zastava Arms as the PBG 40 mm, and Georgia's STC Delta produces its own examples.