A bump stock.

When you watch shaky videos of Sunday night's mass shooting in Las Vegas, one thing stands out: the sound. The shots come in quick succession, like a jackhammer, followed by a few seconds when the gunman presumably was reloading. The crowd is sprayed with unceasing pulses, hundreds of rounds translating into lost and maimed lives.

As you watch, helplessly, all you can think is, "When is this sound going to stop? Please, for the love of God, someone make it stop!"

The gunman, 64-year old Stephen Paddock, was able to fire off so many shots in succession because he had altered his legal semiautomatic rifles with what could have been two "bump stocks," which can be purchased legally that enables a rifle to shoot up to 700 rounds per minute.

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That is why Paddock's gun had the sound of a fully automatic machine gun, a type of weapon heavily regulated since the 1930s. The 1986 National Firearms Act made manufacturing, owning, or transferring automatic weapons all but illegal, requiring those who own automatic weapons manufactured before the act to pay exorbitant fees and pass extensive FBI background checks. As a result, since the gangster era of the 1930s, automatic weapons have rarely been used in the commission of crime in America.

Yet if society has agreed that automatic weapons should be banned — as even many pro-Second Amendment groups do — it makes no sense to allow the sale of a part that circumvents this long-standing prohibition. With a quick Internet search, anyone can find either a "bump stock" or a "trigger crank" to add to a semiautomatic rifle such as an AR-15, allowing it to mimic a machine gun. YouTube is rife with videos explaining how to install and operate these add-ons; one retroactively macabre video instructs users to find the bump stock's "happy spot" before gleefully firing off dozens of high-speed rounds.

Of course, as is the case after every mass shooting, both sides of the gun debate ran to their ideological corners, automatically reciting their well-traveled talking points. While first aid was still being applied to the Las Vegas victims, Hillary Clinton tweeted her opposition to making gun "silencers" easy to get — despite the fact that silencers aren't all that effective on high-capacity, rapid-firing guns such as the ones Paddock allegedly used. The Internet overflowed with accusations that the National Rifle Association "owns" Congress because it has donated $3 million to candidates over the past two decades — a comparatively microscopic amount invoked only to stoke the fears of low-information observers.

But even gun enthusiasts should drop their opposition to devices that make a semiautomatic weapon fully automatic. If the law already bans guns that fire more than one bullet with one squeeze of the trigger, it also should apply to devices that allow that type of rapid firing to take place. If altering the mechanics of a semiautomatic rifle to make it automatic is illegal, then how can it possibly be legal to purchase a $50 part to do the same?

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Gun groups could apply the same argument to bump stocks that they do to gun regulation as a whole. Banning guns doesn't mean they go away; they just fall into the wrong hands. But to date, the almost absolute ban on automatic rifles has been pretty effective, as their use is exceedingly rare. Bump stocks and trigger cranks make a mockery of that.

Naturally, regulating the sale and possession of conversion parts isn't a panacea for gun violence. If Stephen Paddock had been using a semiautomatic rifle rather than a modified automatic, he might still have killed dozens of people when he opened fire on the country music concert in Las Vegas. But he probably wouldn't have been able to kill 59 citizens — many of whom would likely still be around had he not had such easy access to parts that enable mass slaughter of innocents.

Christian Schneider is a columnist at the Milwaukee Journal Sentinel, where this piece first appeared

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