At this point I not believe the gun control legislations are not going to be helpful because there are already too many military grade combat weapons in this USA.
A surprisingly large number of those such guns are legally held and so are "on record" somewhere; with new laws presumably the law-abiding owners would hand them over. New, serious laws might also bring about new attitudes.
I have also noticed that many "ordinary", "public" discussions about gun ownership tend to focus on just the guns. Beyond the serious strictness, such as regular checks on mental health, I think there's something in Japan's gun laws that as well take a tough attitude on
ammunition, without which a gun is useless.
Oh, while the regulations might be somewhat lax on "military-grade" assault rifles, which quite a few people buy for "target practice", the US does have some very strict gun regulations that seem to work. If I recall correctly, a shotgun that is to be used in hunting duck or wild fowl must not be capable of holding more than three shells and cannot be modified in this or that way etc. (
Federal).