Please add in the BAR or Browning Automatic Rifle, 20 round magazine fully automatic, sold by mail order after WW1, used all the way through early Vietnam.
Also the THompson machine gun of the early 1920s. Same.
Some time if you want I can give you a list of European automatic weapons sold here in the USA, Maxim machine gun, MP38, MP40, British Sten, and on and on.
Progressives have no idea of history,