Mp40(MachinePistol 1940) is a submachine gun that fires 9mm and only auto. Besides Stg 44 is worlds first true assault rifles which comes from the german name: SturmGewehr. Besides The Commie Russians stole the plans for the Stg 44 and made the Ak47 out of it. Look at the specs.
StG44
Caliber: 7.92x33 mm (7.92mm Kurz)
Action: Gas operated, tilting bolt
Overall length: 940 mm
Barrel length: 419 mm
Weigth: 5.22 kg
Rate of fire: 650 rounds per minute
Magazine capacity: 30 rounds
Muzzle Velocity: 650 m/s
Ak47
Caliber 7.62x39 mm
Action: Gas operated, rotating bolt with 2 lugs
Overall length: 870 mm
Barrel length: 415 mm
Weight, with empty magazine: AK 4,3 kg; AKM 3,14 kg
Magazine capacity 30 rounds (40 rounds box magazines and 75 rounds drums from RPK also may be used)
Cyclic rate of fire 600 rounds per minute
Maximum effective range: about 400 meters
Effective Range: 450m
Look at the pics:
Ak47
STG44
Russians stole the plans from WWII when then raided a bunch of munition factories. LOOK AT IT!