Moda, everything (except for nuclear weapons) you mentioned in that paragraph WAS at least technically legal to own (at least by Federal law...state laws may have been more restrictive) until the GCA in late 1968 and we had no problems with people being grenaded or howitzered to death in the streets. Bazookas, mortars, surplus WWII artillery, and the like were sold (in some cases by mail order catalog) under the same Federal legal restrictions as any single shot rifle. Grenades were not "destructive devices" and were Federally legal to own as well (again, pursuant to any local or state laws) and explosives like dynamite were sold over the counter in many rural hardware stores to anyone who was 18 and above.If the goal is to match the federal government first and foremost, though, shouldn't we be legalizing far, far more deadly weaponry than smg's? Mines, bombs, tanks, armed fighters and choppers, rocket launchers, grenades, nukes, etc... Where does it stop?
We didn't have an epidemic of mass murders with any of the abovementioned weapons/explosives back then despite their easy availability and if we relegalized/deregulated them now I don't think it would cause any major harm.