Earlier quoted context omitted.
Of course there is. There are legitimate reasons for owning a rifle in rural America (hunting), there are no legitimate reasons for owning an assault weapon, and guns can easily be made gradually less attractive. If you don't accept this even as a possibility you are part of the problem.
What do you think that way (of the government collecting 300m firearms) might be?
This has been done after wars for example (after WWII), and after many different conflicts in different countries in Africa. It would take a long time and would require tightening laws gradually and at the same time encouraging people to hand in their weapons.
This is not particularly difficult logistically, the only difficulty is in the American psyche apparently, which seems completely incompatible with this simple common-sense measure. The outcome would be fewer deaths by cop, fewer deaths in burglaries, and fewer mass shootings.
There is abundant evidence from around the globe that limiting the ownership of guns helps limit deaths.