Question: What type of gun was attempted to improve in The Heckler & Koch MP2000?
Context: The Heckler & Koch HK416 is an assault rifle/carbine designed and manufactured by Heckler & Koch.  Although its design is in large part based on the AR-15 class of weapons, specifically the Colt M4 carbine family issued to the U.S. military, it uses an HK-proprietary short-stroke gas piston system originally derived from the ArmaLite AR-18 (the same system was also used in Heckler & Koch's earlier G36 family of rifles).  The HK416 gained fame as the weapon that United States Navy SEALs from DEVGRU Red Squadron used to kill Osama Bin Laden in 2011. Alex Seidel (4 July 1909 – 24 October 1989) was a German weapons manufacturer and the co-founder of Heckler & Koch along with Theodor Koch and Edmund Heckler.  Together the three men built the Heckler and Koch company out of the old name of Heckler & Co. on December 28, 1949. The Heckler & Koch MP7 "(Machine Pistol 7)" is a German Personal Defence Weapon (PDW) designed and manufactured by Heckler & Koch (H&K) and chambered for the HK 4.6×30mm cartridge.  It 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 penetrate 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 latest production variants are the MP7A1 and MP7A2. <ref name="Heckler & Koch HK MP7 Submachine Gun / Machine Pistol July 30, 2012"> </ref> The Heckler and Koch HK43 is a semi-automatic rifle based upon the Heckler & Koch HK33 rifle and is the predecessor of the Heckler & Koch HK93 semi-automatic rifle. The Heckler & Koch MP5 (from German: "Maschinenpistole 5" , meaning "Submachine gun 5") is a 9mm submachine gun of German design, developed in the 1960s by a team of engineers from the German small arms manufacturer Heckler & Koch GmbH (H&K) of Oberndorf am Neckar.  There are over 100 variants of the MP5, including some semi-automatic versions. The G41 is a German 5.56×45mm NATO assault rifle introduced in 1981 and produced in limited quantities by Heckler & Koch.  It was designed to replace the 5.56mm Heckler & Koch HK33 in service providing a more modern weapon compatible with contemporary NATO standards.  It is chambered for the 5.56×45mm NATO cartridge and can use both SS109 and M193 ammunition.  Assembly of the G41 has been discontinued by Heckler & Koch, however, production rights to the rifle were acquired by the Italian arms manufacturer Luigi Franchi. The Heckler & Koch MP2000 was an attempt to improve the MP5 series.  Prototypes of the gun showed similarities to the UMP.  An interesting feature of this gun was that it featured a silencing system which prevented the bullet from reaching supersonic speeds by venting some of the propellant gases.  The gas vent hole could be closed in order to achieve normal bullet velocities. The Heckler & Koch HK41 is a semi-automatic version of the Heckler & Koch G3 battle rifle; it was produced by Heckler & Koch for the civilian market in the 1960s.  It is not to be confused with the similarly titled Heckler & Koch G41. The Heckler & Koch HK CAWS (H&K CAWS) is a prototype automatic shotgun—designed as a combat shotgun—co-produced by Heckler & Koch and Winchester/Olin during the 1980s.  It was Heckler & Koch's entry into the U.S military's Close Assault Weapon System program. The Heckler & Koch HK45 ("Heckler & Koch, .45 ACP") is a semi-automatic pistol designed by the German arms manufacturer Heckler & Koch.
Answer: 9mm submachine gun