This gun paper model is a Heckler & Koch MP7, a German Personal Defence Weapon (PDW) manufactured by Heckler & Koch (H&K) and chambered for the HK 4.6×30mm cartridge, the papercraft is created by Sasha Meyson.
The MP7 was designed with the new cartridge to meet NATO requirements published in 1989, as these requirements call for a personal defense weapon (PDW) class firearm, with a greater ability to defeat body armor than current weapons limited to conventional pistol cartridges. The MP7 went into production in 2001. It is a direct rival to the FN P90, also developed in response to NATO's requirement.
The weapon has been revised since its introduction and the current production versions are the MP7A1 and newest MP7A2. The proliferation of high-quality body armour has begun to make guns that fire pistol ammunition ineffective. In response to this trend, Heckler & Koch designed the MP7 to penetrate body armor, but small enough to be used in place of either a pistol or a submachine gun. More information at wikipedia.