<< I thought the difference between Submachine guns and Machine Guns was the fact that the SUBmachine guns shoot bullets that are SUBsonic. This is what I was told when I toured the FBI building a few years ago... so correct me if I am wrong. >>
Well, apparently your tour guide had been in the evidence locker using some of the confiscated drugs. A submachine gun is smaller than a machine gun, meant to be used by one man, rather than as a crewed weapon, which when the term was invented, all, or at least almost all "regular" (those not designated light or heavy) and heavy machine guns were crewed by more than one man, and even most "light" machine guns were crewed as well. A submachinegun was a new development... fully automatic weapons in the hands of one man... much more mobile than a regular machine gun, didnt need a bi-pod or a tri-pod... the advantages of all that should be obvious. To the best of my knowledge, no submachine gun is belt-fed. Most/all machine guns are belt fed (yes, I know the 5.56mm SAW can use magazines from a M-16, but thats just for interoperatibility, its preferably used with a belt). One exception to that last sentence that I can think of was the Lewis light machine gun... it used a funny looking drum magazine, but that was fairly early in the development of the machine gun.