Fully foreign automatics manufactured after 1986 are already illegal to buy or own, so let's start with those imported before the cutoff. Then, ban all semi autos such as the Glock 17. Next, go the the semi automatic rifles, before banning and confiscating all revolvers, pistols, muskets, Saturday night specials and miscellaneous handguns. 420 million guns sounds like a lot, but every journey begins with a small step, and Americans are a law-abiding people. I am sure that the 59% of households in Wyoming [that are gun-owning] for example would cheerfully hand over their ordnance to government agents. I'll bet though that the 3.8% of DC residents that fess up to having "a tiny little gun" will bitterly cling to their sidearms as the homicide rate there is 22/100,000. (Oddly, Wyoming's murder rate is 1.4/100,000 or about 6% of DC's - go figure!) Anyway after we've rounded up all those armaments and those hunting rifles that are always lickin' off at inopportune moments, it's only a beginning - knives over certain lengths, switchblades, stilettos, boker knives - these bad bad things only have one purpose and we don't need 'em in a free society.
I hear Google's working on a driverless car. Good. Til' then, a GPS activated speed governor on each vehicle will make us safer. We need to rubberize rocks and bottles, too.
We won't rest until the children are able to walk down the street without fear of a crazy man with weapons.