By and large, submachine gun class weapons were largely designed around existing pistol-type cartridges which, for their time, offered good man-stopping capabilities as targets were generally unarmored. However, throughout the 1980s, body armor technology allowed users wider access to lighter - yet still effective - protection which inspired new breeds of cartridge - and corresponding weapons - to take shape. NATO saw a similar need and issued a 1989 charge for such a cartridge, prompting several competing firearms firms to develop new solutions.
One submission became the Heckler & Koch HK MP7 chambered for the HK 4.6x30mm cartridge. The HK firm of Germany had long held a lead in the submachine gun market, their HK MP5 submachine gun (chambered in 9mm) becoming its ubiquitous product line. the HK MP7 followed the tried and proven measures that made the MP5 such a successful weapon including use of heavy duty composites and attention to design. However, the MP7 would be keenly different from the preceding MP5 design for it was intended to function as a machine pistol, submachine gun and "personal defense weapon" (PDW) all in one. Therefore, it could be issued to special forces operatives, paratroopers (airborne soldiers), security personnel, police units and second-line/logistical troops without loss of firepower.
The HK MP7 is, therefore, very compact and can be utilized in a traditional three-point hold (two-handed and up against the shoulder) or a standard two-hand hold as with a pistol. The weapon is relatively light-weight at 2.6lbs unloaded and maintains a running length of 25 inches. Utilizing the collapsing stock, the weapon can be brought down to a more manageable 16 inch length when space is a luxury. The barrel itself measures in at 7 inches while the receiver, at its thickest, is just 2 inches wide.
The key design element of the HK MP7 is the proprietary HK 4.6x30mm cartridge. The cartridge was first introduced in 1999 and began widespread use in 2001 is of a rimless bottleneck design. Its design is such that the cartridge offers very little recoil yet can still penetrate armored subjects at range - the smaller diameter being the driving quality here. Since its inception, the cartridge had evolved into a family of solutions including the basic penetrator, a hollow point offering, and a full metal jacket design. The HP MP7 is the only weapon that currently makes use of the HK 4.6x30mm cartridge aside from the cancelled HK UCP pistol. All told, the HK MP7 and UCP were direct competitors to the Belgian FN-Herstal FN P90 submachine gun and Five-Seven pistol - these chambered for the proprietary 5.7x28mm cartridge.
HK utilized the action of their successful HK G36 assault rifle in the HK MP7, this being a gas-operation system utilizing a short-stroke piston with a rotating bolt assembly. The prototype was known as the PDW (Personal Defense Weapon) and debuted in 1999. After a period of evaluation, it entered serial production under the company designation of HK MP7 in 2001.
The MP7 is given a rate-of-fire of 950 rounds per minute with a 2,400 feet per second muzzle velocity. Effective range is approximately 200 meters. The weapon can be fed from a 20-, 30- or 40-round detachable box magazine, this being inserted in an UZI-style magazine well that makes up the pistol grip handle. Firing controls (selector, safety) are all ambidextrous to accommodate left- and right-handed users. Sighting is through a front and rear folding/adjustable iron sight installation as well as a Tritium-illuminated flip-up type night sight.
The external design of the HK MP7 series is typical Heckler & Koch, utilizing sharp clean lines in an all-black finish. There are Picatinny accessory rails along the top of the receiver and both sides (newer model) of the forend. The gas cylinder is mounted over the barrel which is largely shrouded by the forend cover. The magazine/pistol grip is mounted near the center of the design for a good balanced hold. This lets the rear of the receiver come over the forearm to which the stock is fitted. Being collapsible in nature, the stock can be brought in or pulled out as needed. One design feature of note is the folding forward vertical grip that is hinged to collapse along the underside of the forend, just ahead of the trigger. The trigger itself is encased in an oblong ring that allows use of a gloved hand. The fire selector switch is easily found near the thumb with the typical HK graphical settings in white and red. The single white bullet indicates the safety while the single red bullet allows for single-shot, semi-automatic fire. The four inline bullets indicate full-automatic fire.
The HK MP7 is designed to accepted a variety of tactical accessories including a sound suppressor over the barrel, flashlights, laser aimers, reflex sights and various scopes.
The MP7 design was updated with a new grip, smoother contours, side-mounted Picatinny rails and revised stock in 2003. From this point on, it carried the company model designation of "MP7A1". There exists a semi-automatic-fire-only version of the weapon - the "MP7-SF". Production of the MP7 continues as of this writing (2012).
To date, the MP7/MP7A1 is utilized by Albania, Australia, Austria, Croatia, Germany, Ireland, Italy, Jordan, Malaysia, Norway, Oman, South Korea, the United Kingdom and the United States. Many are being issued to special forces groups or police units. The weapon has seen combat actions in Afghanistan since the American-led invasion of 2001.