In recent years I’ve thought about getting armed. I’m not a pacifist, and I live near Crazytown. I don’t expect I would prevail in a gunfight, but I do think I could take a few miscreants with me. I earned an NRA Sharpshooter badge in summer camp, in about 1959. Target shooting was great fun. I’m aware of stats about the dangers of individual ownership, but I don’t think they apply to me. I’m not a klutz, and we don’t have kids in the house. We hardly even have visitors. Still, I’d also be happy to abide by any firearms restriction you might think of, if it became law.
You are on the money.
See also restricting long gun purchases to those 21 and older. Josh Marshall of Talking Points Memo has a note supporting this. He observes: "Perversely, federal law requires purchasers of handguns to be 21." His note is at https://talkingpointsmemo.com/edblog/a-possible-glimmer-of-hope-amidst-the-wreckage.
"Assault rifle" is impossible to define, but "semiautomatic gun" is pretty easy. If somebody wants to dress up a bolt-action gun with all kinds of manly paraphernalia such as Picatinny rails or engravings of Donald Trump, who cares?
Really there is phrasing that would phase out assault rifles that is non-loophole proof but low loophole. "No gun shall be sold capable of firing more than rounds of ammunition (make it ten if you wish) without reloading, nor easily modified to become so capable. Nor shall any bump stocks or other accessories be sold that increase the ammunition capability of such weapons, nor that allow reloading in less than 60 seconds. (Again final number of seconds to be set after consultation with experts.) No gun shall be sold capable of accelerating shots to a speed of more than X miles per hour." If you limit the number of rounds and the speed of ammunition, meaning the distance at which you shoot people, you pretty much eliminated the characteristics that make assault rifles worse than shotguns and handguns.
Until you can guarantee that gun control can remove guns from the right wing crazies and fascists bent on oppressing all who are not like them, the value of these efforts will be nil.