If you want a model of just how dangerous it is to have your country saturated with fully-automatic weapons, take a look at Switzerland. Their army is a cross between a regular army and a militia. Men are conscripted at the age of 19 and those that don't fulfill their service all at once stay in the military for years, serving a few weeks at a time. The important thing to note is that they take their fully-automatic assault rifles (and ammo) home with them so they can be mobilized as quickly as possible if needed.
In the US, the violent crime rate is 713/100,000 people, and in Switzerland is is 86/100,000 from a UN study of crime rates published in Singapore.
http://www.singstat.gov.sg/ssn/feat/4Q97/feat.pdf
Maybe we should all get machine guns to help get the US crime rate down.