I got all but the barrett right, it looks like a knock off from the one I have shot.
A bit of history...
The Maschinenpistole 43, Maschinenpistole 44, Sturmgewehr 44 (MP43, MP44, StG44 respectively) were names for a light automatic rifle developed for Nazi Germany during World War II as part of the Maschinenkarabiner (machine carbine) program, and developed from the Mkb 42(H). The many names of the Mkb 42(H)'s successor result from the complicated events in the bureaucracy of the Third Reich.
The MP43, MP44, and StG44 were names for nearly identical weapons with only small production differences and dates. The last, the StG44, was called "Sturmgewehr", literally, "storm-rifle" (or assault rifle). It combined the traits of submachine guns and automatic rifles. The translation "assault rifle" became very popular to describe this class of weapon, but it was far from being the first of this type.
It chambered a shorter version of the standard 7.92 mm rifle round, which, in combination with the weapon's design allowed it to be used like a submachine gun in close quarters but with greater accuracy and range than submachine guns in longer range engagements. However, it had much less range and power than regular rifles of the day; fortunately, at that time, much of the fighting was taking place at closer ranges such as in towns, cities, and wooded areas.
It was a popular weapon; much of the Wehrmacht was armed with either submachine guns or bolt-action rifles such as the Karabiner 98k, and only a limited number of soldiers were issued the semi-automatic rifles. There was also a distinct lack of a dedicated light machine gun (LMG). The MG34 and MG42 had versions that were meant to serve in this role but they were on the heavy side for a LMG. The StG44 was not a light machine gun, but it did fill the need for a light automatic rifle that offered mobile suppressive fire, like the Bren, while at the same time offering much of the convenience of a submachine gun or light automatic rifle.
A light automatic rifle, the FG42, was available for paratroopers as a semi-automatic rifle and light support weapon. However, it was produced in only a few thousand units because it was not economical to manufacture and due to internal politics of the Nazi government.