I believe in the realm of US semi/full auto arms of ww2 the breakdown would be
M1garand 30.06 battle rifle
browning BAR 30.06 light machine gun
M1carbine .30carbine assault rifle?submachine gun? in modern verbiage a pistol caliber carbine? the M2 was select fire so full auto back to submachine gun?
M2 browning .50 heavy machine gun
Thompson/colt .45 submachine gun
M3 .45 (grease gun) submachine gun
the biggest advantages to submachineguns is lighter/smaller ammo so you can carry more and high rate of fire with lower recoil so you can shoot it faster and stay on target.
an "assault" rifle was first fielded (though too late) by ww2 germany. it had most of the advantages of a submachine gun but kept a decent sized round to be more effective at ranges further than typical sub-guns could .
that paved the way for the greatest battle implement ever devised ….AK47
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The more you run over a dead cat,
the flatter it gets.
-Anonymous