I can tell there is a solution it is very costly, try the Australian solution an amnesty and buy back where every surrendered weapon is valued and paid for and destroyed and no questions asked, and from that point on no military weapons, no semi automatics allowed, all weapons licensed, and secure, no carry permits except for cops and licenced security and no concealed weapons and just maybe you need a change to the constitution rewording the second amendment
You could even have a gun buy back led recovery with a lot of cash flowing from disused and surrendered weapons. just think 280,000,000 weapons at say $500.
How about you start with this solution
Adelaide mum Sam Paior plans toy gun 'buy-back' after Sandy Hook shootings in Connecticut | News.com.au