Actually, the old Tommy was the best SMG the Americans built in huge quantity.
The M-3 had that cute little crank on the right side, but it was susceptible to damage if you beat the gun around.
M-3 was replaced by M-3A1, which got rid of the crank and had NO cocking mechanism. You had to stick your FINGER inside the thing and reef back on the Bolt to #### it! I emphatically do NOT like putting my hands inside an operational firearm which happens to be loaded! At 350 rpm cyclic, you could just about have a smoke between shots!
America's forgotten SMG was the Reising Model 50, a .45-cal gun with 12- and 20-round magazines and a concealed cocking-bar under the barrel, hidden in the stock. Reisings fired from a CLOSED bolt and are blistering accurate. For some idiotic reason, the Bolts were never numbered....... but the gun REQUIRED the correct Bolt in order to function its best. I have fitted Bolts to a couple and they have come up super-reliable. My own gun's Bolt fits fine; the gun is accurate and reliable. The 11-inch barrel gave you an extra 200 ft/sec as well. Somebody should have done a quick redesign on the Reising to give the trigger mech a metal cover, then added a folding stock a la Schmeisser. It would have made a superb gun. As was, they only built just over 111,000 total. Last sale was to Venezuela, which got the highest-numbered guns. Pity.