The purchase of fully automatic weapons has been tightly restricted in the U.S. since the 1930s. Outlaws great and small used fully automatic weapons (machine guns and sub-machine guns) against rivals and against the police. The 1934 National Firearms Act narrowly restricted ownership of fully automatic weapons; a 1986 amendment prohibited most transfers or possession of automatic weapons, except those that had been manufactured and registered with the government in the past. It would appear that most privately-owned fully automatic weapons are in the possession of licensed gun-ranges. You can go to a range, pay a daunting fee, and fire a fully automatic weapon at a paper target. That’s enough for most gun-owners
Still, a small number of gun-owners yearned for the experience of firing a weapon on full-auto at a lower cost. Then, some physically-disabled shooters wanted an adaptive technology that would allow them to enjoy one of their favorite pre-disability sports. Admittedly, this is kind of a niche market. Numerous attempts to design retrofits for semi-automatic weapons failed. Then, in 2008 or 2009, someone invented “bump stocks.” The particular technology doesn’t seem to me to matter. The effect does matter. “Bump stocks” allowed shooters to “simulate” full automatic fire.
In 2010, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (commonly ATF) considered whether they violated federal law by creating a new form of fully automatic weapons. ATF concluded that they did not violate federal legal restrictions on automatic weapons. They did not alter the internal firing mechanism. They just exploited it to achieve the same effect as a full-auto weapon. So, “bump stocks” were good to go. This was two years before the Sandy Hook Elementary School shootings. In the wake of the Sandy Hook shootings, President Obama said he would “use whatever power this office holds” to prevent a new version of the massacre. Alas, when he issued 23 Executive Orders in January 2013 to enhance gun-control, these did not include ordering ATF to revisit its approval of “bump stocks.”
Still, “bump stock”-modified weapons have problems. First, they are Hell on accuracy. Still if a sniper has 22,000 people penned inside a concert venue, s/he doesn’t need to be very accurate. Anything within range can become a target. Second, firing weapons designed to fire as semi-automatic on “simulated” full-auto generates more heat than the weapons are designed to handle. They tend to jam. So Stephen Paddock attached “bump stocks” to 12 of the rifles he brought to his room in the Mandalay Bay. It seems likely that he walked back and forth between the two windows he had broken whenever a weapon jammed, picking another off the bed on the way.
The obvious solution here is to revisit the 2010 ATF decision and declare “bump stocks” illegal. That won’t do the casualties in Las Vegas any good, but it might help forestall mass shootings in the future. Still, “mass shootings” as conventionally defined and long-guns (rifles and shotguns) account for a small share of the murders and suicides that still give America a high homicide rate. Certainly, action on this front is needed. It should not distract people from the much larger problem of hand-gun killings. However, it will do just that. For now.
 Kind of like “legacy” admissions to Ivy League universities. I don’t mean to suggest that they have equally harmful effects on American society.
 One Georgia gun-dealer judged that he had sold a couple in a couple of years.
 At maybe $200 each, that cost his about $2,400.