Despite the discomfort some might have over private citizens owning guns that were made for soldiers, law enforcement authorities say they can't point to a specific instance in which a legally registered machine gun was used by a private citizen to commit a violent crime.
The weapons used in Connecticut, at Sandy Hook Elementary School, and in Colorado, at an Aurora movie theater, for example, were lesser weapons, semiautomatics that are quickly and more easily purchased at sporting-goods stores, whereas obtaining a license for a machine gun takes six months.
Larry Karson, an assistant professor of criminal justice at the University of Houston-Downtown and a retired federal agent, said regulations and culture surrounding fully automatic weapons are an example of successful gun control, with respect to safety.
"You haven't had any violations of consequence to make it a front-page story to change the law," he said, adding that the government can confirm the whereabouts and ownership of machine guns through a home visit, if needed.
"A gun dealer who handles these types of weapons is as concerned about the safety of a community as any law-enforcement officer," he said.
The number of such guns was limited after President Ronald Reagan signed a law stipulating no more new machine guns, starting in 1986, could be produced for civilian ownership. The move was born from a 1934 law that first required machine guns be registered with the government and established a $200 tax. The restriction was meant to rein in Tommy guns from the gangster days.
The tax was a purposely stifling amount back in the day, but remains the same even now, although if it were adjusted for inflation, it would equate to $3,436, today, according to the Department of Labor.
Every year, there are slightly fewer guns circulating, so their price climbs and with time, more collectors seek them. The price of an M-16 before 1986 cost about $800, and now goes for about $20,000.