See Part II here: https://www.full30.com/video/100df1b53fa560da2efd6bc419cc6375
The MP-43 (which is mechanically identical to the MP-44 and StG-44; the differences are the subject for another video later) is a tilting bolt rifle with a long stroke gas piston. It was manufactured primarily from complex sheet steel stampings, as a way to minimize the amount of high-quality and thus difficult to acquire steels needed for its construction. The rifle is heavy by today's standards, but remarkably ergonomic (except for the metal handguard, when heats up quickly). Its sights come right up to the eye when shouldering the rifle, and it disassembles quickly and easily.
It really is one of the best small arms developed during World War II.
Sturmgewehr vs Kalashnikov: https://www.full30.com/video/5a5e03f95d231d7e1497e60c286cd595
MkB-42(H) with ZF41: https://www.full30.com/video/ecb06609072596f08e294235185ae9c9
StG-44 with Krummlauf: https://www.full30.com/video/0b8f8c4dc05119c30016e8974f6d5103
VG1-5 Last Ditch Nazi Rifle: https://www.full30.com/video/8cf42b984258db76bb96eb123aa52591