With 3D printing of basic weapons now possible, taking care in the sale of ammunition is more important as that can't be printed.
As for gun laws in general, the situation in the US is different to Australia. Criminals can buy military grade weapons at any US gun show legally, and the country has been flooded with guns since the 1990s, when the Republicans weakened gun laws and banned scientific research into issues of availability and gun crimes. End result is it's too late for them now. Too many guns in the hands of criminals, nutters and overly excitable people.
Thanks to John Howard we went the other way in the 1990s and concentrated on law and order rather than arming the populace for self-defence. Looking at the US figures on shootings, IMO Howard saved the lives of thousands of Australians by strengthening gun laws in Oz.
