The Heckler & Koch Machine Pistol model 5 (called 'Viper 5' in-game) is a sub-machine gun of German design based on the G3 battle rifle. It is featured in the entire S.T.A.L.K.E.R. series. The Viper 5 is used primarily by Rookie members of several stalker clans.
The view model used in Stalker is the variant HK54, later known as the MP5A1, which was the first prototype of the MP5 series made in the 1960s. As a result, it is cheap and abundant in the black-market, therefore also making its way into the zone.[source/verification needed] The lightweight and compact design gives this weapon great handling statistics. The aperture-type iron sights make the weapon easy to aim, and is relatively controllable on fully automatic.
Like all MP5s, the weapon comes in with an SEF trigger system, it is capable of single shot, 2 shot burst, 3 shot burst and full auto. The weapon uses 9x19mm ammunition and has 30 rounds per magazine. The weapon's light weight, cheap ammunition and reasonably strong damage makes it a good alternative to shotguns as it features better effective range at the cost of burst damage. The gun features a "stick" magazine and a telescoping stock. It can be fitted with a suppressor.and it 's weight is like the sa avalanche
The 9x19 ammo is a very common round, making it a useful weapon against rookie and experienced stalkers equipped with sub-par weaponry. However, it will eventually outlive its usefulness due to its low powered nature, though it is still useful against most mutants due to it's good stopping power and high fire rate. While the 9x19mm round is available in FMJ varieties, the round still does little against adversaries wearing medium armor or above ( example, it will normally take up to 400 rounds to kill a CPU wearing an exoskeleton-equipped NPC, on easy dificulty ). The weapon is effective against unarmored or lightly armored Stalkers, like Bandits. It is also effective against mutants and is very controllable, even when fired on fully automatic. The weapon is relatively accurate and can be used against certain armored foes if the user can achieve headshots. It may serve as a useful alternatives to shotguns thanks to its range, rate of fire and good performance in close quarters. It, due to its low weight and corresponding ammo's low weight make it desirable as an emergency back up automatic.
It's sold by a variety of traders and ammo for it is common found or cheaply purchased, making it a powerful weapon in the first to mid parts of the game. 9x19 ammunition can be rare at first, but the weapon can be converted by most technicians to fire the extremely common 9x18 round instead and 9x19 ammuniton can be purchased from almost any trader. It can be found very early in the game, on a table in the pump station in the Swamps, though sometimes a Renegade defending the area will pick it up. The weapon is also sometimes used by Renegades in the northeastern corner of the swamp, past the machine yard.
It can be upgraded by most technicians and made surprisingly more powerful than assault rifles. However, its lack of upgrades and additional add-ons (excluding the Silencer) will eventually wean its use. It is still however an invaluable starter weapon, especially since it can be modified to use the more common 9x18 cartridge. Compared to assault rifles, like the AK-74 and LR 300, the Viper 5 surprisingly has better damage and its accuracy is rivaled by the LR 300. Its firing rate is also slightly higher than the two. However, as previously stated, it only has the same upgrades of the AKSU-74, which limits it's maximum potential; along with its maximum effective range. Furthermore, its low powered ammunition cannot efficiently penetrate light body armor, making it virtually useless against better armed targets like those wearing an Exoskeleton or a Berill-5M Armoured Suit. Anyone with a bulletproof protection of 30 points can withstand several shots from this weapon before dying. It still remains useful against mutants since they have no armor (the only exception is a Pseudogiant, which has heavy natural armor).
The Viper 5 rivals many assault rifles in stats and against unarmored enemies is simply a better weapon than the AKM-74/2. The 9x19 (or 9x18 with an "upgrade", although 9x18 is actually more rare in CoP) ammo's low armor piercing performance compared to any of the rifle rounds, however, means that the Viper 5 is not particularly effective against armored human opponents, though it remains devastating against mutants. The unique version Frasier fires .45 ammunition and does not have the same problems against armored enemies, though it suffers from a far less common ammunition type.
These guns are quite old: by 1977, most MP5 guns use curved mags, however calibers like the .45 and .40 variants will use straight magazines for easy feeding.
The gun is still in production in low numbers, with all its different variant from the suitcase mini version to the fullsized version, its used mainly by police and security officers. Its being phased out in Latin- and South America where it has been manufactered under license.