Government was designed to establish order and create solutions for a flawed society.
Instead of banning assault weapons, or doing nothing at all, establish a system that creates a gray area.
For instance, allow the purchase of assault weapons and ammo from government institutions, but keep them locked up and guarded in a local facility such as a a police station or National Guard post, along with the weapon's characteristics (serial number, round size, etc.).
When a citizen wants them, the individual must sign them out using identification, official forms and records, and a legit reason such as recreational use or for a national crisis.
Minor weapon's should not be affected. This includes pistols, shotguns, and rifles. They are most commonly used for personal protection or hunting.