The Heckler and Koch MP5 is a popular and famous sub-machinegun, dating from 1960. Although H&K failed to interest Germany's armed forces in the MP5, it was introduced in German police service in 1966 as the
Heckler and Koch 5
4, which, in Heckler and Koch's internal notation, stood for 'Machine-Pistol, Submachinegun,
9mm'. With body armour being more sophisticated than it was in the 1960s, the gun was also chambered for
10mm and
.40 rounds, and is therefore universally referred to as the MP5. Nowadays it is only available in 9mm, but the name has stuck.
Technically, the gun is a closed-bolt, delayed roller-locked blowback firearm, derived from the Heckler and Koch G3 battle rifle. The majority of modern self-loading rifles operate their mechanism with gas tapped from the barrel; the G3 and MP5 use straight recoil as an impelling force, with a clever arrangement of rollers which hold the chamber shut until the gas pressure has fallen within safe limits. As with other H&K products, the MP5 is 'modular', in that the various basic components of the weapon can be interchanged. There are versions with retracting stocks, no stocks at all, short-barreled compact versions (the MP5K), a version with an integral suppressor (the MP5SD), even a version that can be concealed and fired from within a special briefcase. Furthermore, there are a variety of 'trigger groups' which enabled different combinations of semi-automatic, fully-automatic or multiple-round burst fire.
It is used widely by counter-terrorist forces, most famously Britain's Special Air Service regiment. Television footage of the Prince's Gate embassy assault in 1981 showed black-clad SAS soldiers blowing open windows, armed with MP5s. Heckler and Koch could not have bought better advertising had they tried and, since then, the MP5 has become something of a status symbol amongst police and security forces. Most of Britain's armed police forces, including London's SO19, use MP5s. You might think that such people would be above that kind of petty points-scoring, but no. The SAS originally used a variety of weapons, including the Ingram MAC 10 - long before it became notorious in the hands of criminals. The MP5 was adopted in the late 1960s for a variety of reasons, including H&K's financial stability, the weapon's reliability, and the fact that it fired from a closed bolt, which reduces the chance of an accidental shot if the gun is dropped or struck. Heckler & Koch were also more than willing to accomodate their customers' wishes, and have produced many 'special editions' of the MP5 for different governments and military organisations. If one of your friends happens to become the chief armaments minister of Eritrea, you know who to call (although Fabrique Nationale of Belgium might also want to speak to you).
Since then the MP5 has also appeared in countless films as a 'classy' weapon, usually in the hands of well-dressed terrorists or drug-runners, most notably in the first two Die Hard movies. In this respect it has supplanted the Uzi, which had a similar hold over Hollywood's imagination in the early 1980s. Heckler and Koch have subsequently replaced the weapon with the UMP, although the MP5 - now knocking on for forty years old - has not dated either in design or functionality. Flesh and bone are still as vulnerable to the impact of supersonic, corkscrewing lead pellets as they ever were.
Apart from being a device used by both police military forcse, the weapon is also popular in the more realistic computer games - the original version of 'Half-Life' used an odd MP5 / Grenade Launcher combination as its 'assault rifle' (something which is technically possible, if extremely unlikely), whilst it is the default option in 'Rainbow Six' and its derivatives.
The MP5 was sold to the civilian market in America during the 1980s as the HK94, although fitted with a 16" barrel to comply with regulations.
Selected sources:
http://www.hkpro.com/mp5.htm
http://world.guns.ru/smg/smg14-e.htm
http://home.hccnet.nl/22.sas/Operation%20Nimrod.html