The primary reason that the Germans had designated the MP-43 and MP-44 as Machine Pistols was that Hitler had declared that all development of rifles and rifle style weapons should cease and small arm development and production concentrate on sub-machine guns. When the MP-44 was shown to be a success and accepted as a valid weapon the Hitler (supposedly) changed the designation to a more appropriate one "SturmGewehr" or StG*

*sometimes incorrectly seen as StuG, which was actually the official designation of a self propelled howitzer designed to give close support to assaults against fortified positions.

THe early US Automaitc rifles were slower than an expert British soldier using a .303 bolt action rifle (a slowly evolving design which originated in teh Crimea War, adn was not finally abandoned until after WWII), although they were faster than raw recruits using Rifle Mk 5's , the final version of the British .303.