Staff Writer (Updated: 7/25/2016):
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.