GP-25

History
The GP-25 Kostyor ('Bonfire') is a Russian under barrel grenade launcher for the Avtomat Kalashnikova 47 series of assault rifles. 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 40-mm GP-25 under-barrel grenade launcher is a standard issue weapon of the Russian Army. It is also used by Special Forces including Spetsnaz, the Federal Security Service (formerly the KGB) and Ministry of Justice. A simplified version called the GP-30 is in use now, and can be fitted on most assault rifles used by Spetsnaz, such as the AN94, OTS-14 GROZA, and AK-74.

In-Game
Laucher used in both Modern Warfare games is GP-30, as evidenced by sights placed on the right side of the barrel. The GP-30 is similar to the M203 in damage and effect although in real life they function quite differently. The main difference is in loading mechanics and design of rounds that it fires. Apart from standard VOG-25 grenade, VOG-25P was developed, that features a small, initial charge which is triggered upon impact. This initial charge launches the grenade approximately 1.5 - 3 meters into the air before the primary fragmentation charge is triggered by the delay timer. This is quite different from the M203's 40mm grenade, which simply explodes upon impact, assuming it has been airborne long enough to arm the grenade. Unlike the M203, the SAS's and Marines' grenade launcher, in which the grenade compartment slides forward to accept/release a grenade shell, the GP-30 simply has a hole in front, which the user snaps his wrist to release a spent grenade, and just drops in a fresh one. It is called "Mortar-like" loading. In reality, the GP-series lauchers use caseless grenades, which do not leave a shell in the barrel. This allows the shooter to simply load a new grenade without spending time to extract a spent case. Although it is seen mounted to an AKS-74U in the armory on the mission F.N.G., it is not a usable attachment for this weapon in Multiplayer, nor is it used by any enemy or ally during the single-player campaign.

Singleplayer
It is an attachment featured on the AK-47 Grenadier used by the Loyalists, OpFor and the Ultranationalists during the Singleplayer Campaign. Sergeant Kamarov is featured using this weapon.

Multiplayer
This weapon is an attachment for the AK-47 assault rifle, both of which are available from the start, although rank 4 is required to make a custom class that uses the weapon. This attachment replaces the tier one Perk. As previously mentioned it is indistinguishable from the M203 attachment in function and damage. The majority of servers and players look down upon the use of grenade launchers as they are extremely effective and require minimal fitnesse to attain kills. It has earned the nickname 'noob tube' and is referred to as such almost exclusively, even by players who use the attachment. Like the M203, it can be used to attain the challenge Ouch by directly hitting and killing an enemy player within the minimum range, which does not trigger the explosive fragmentation, but simply impacts the target.

Modern Warfare 2
The GP-30 is only available for the AK-47, but like the M203 it is possible to get a headshot. If you shoot a grenade and it explodes on contact with your enemies head the headshot indicator will show in the kill indicator. (bottom left)

Trivia

 * During the Modern Warfare 2 reveal trailers the M203 was used as a place holder for the GP-25.
 * An AKS-74U with a GP-25 attached can be seen in the armory on F.N.G.
 * The AK-47 is the only gun in Call of Duty 4 and Modern Warfare 2 to use this grenade launcher. It is not equal stat wise to the M203 in both games: it has a faster switch-to time but a subtly slower reload time.
 * The GP-25 reloads slightly slower than the M203.
 * In Modern Warfare 2, the Militia use a GP-25 as their grenade launcher.
 * Most players prefer to call the grenade launcher a "noob tube" because it can be used to kill another player fairly easily.