In the wake of the mass murder of homosexuals at a nightclub in Orlando, Florida, much attention has been turned to the legal status of assault rifles. These weapons, sometimes easier to legally obtain than a pistol, are semiautomatic — bullets fire as quickly as the user can pull the trigger. This is distinct from an automatic weapon (a machine gun), where the user can hold down the trigger and spray a continuous stream of bullets.

Though there are ways to modify a semi-automatic weapon to make it fire like a full automatic, machine guns are not readily available in the United States, due to a limited supply, strict regulations, and a federal ban.

This wasn’t always the case. In the first decades of the 20th century, machine guns were widely used by the mob, and by criminal figures like John Dillinger, or Bonnie and Clyde. In 1929, the Chicago police estimated Chicago gangs had some 500 machine guns. “It is no trouble to buy machine guns,” V. A. Daniels, a gun runner, told a local newspaper at the time.

After repeated incidents of machine gun violence — such as Bonnie and Clyde’s demise or the St. Valentine’s Day Massacre — the U.S., in 1934, passed the National Firearms Act, which imposed strict requirements on machine gun ownership: there was a huge tax upon purchase (originally $200, which translates to $3,500 in today’s dollars), and buyers had to be fingerprinted, photographed, and entered into a national ownership registry. The measure was even approved by the National Rifle Association, which used to be much more concerned with sensible gun control.

Robert Spitzer, a gun law scholar at the State University of New York at Cortland, says this caused machine gun sales to evaporate. In other words, regulations had a profound affect on the number of machine guns in circulation.

Spitzer told NPR:

It is a good example of something that is little known, which is a gun control law that was pretty effective in keeping such weapons out of civilian hands. So by 1986, when the provision was added to the Firearm Owners’ Protection Act to bar any newly produced fully automatic weapon from possession by civilians, it was really a fairly small step to make, because so few of them were in circulation to begin with.

Indeed, after 50 years of strict guidelines for machine gun ownership (and an essentially doubled price), the U.S. went a step further. While the Firearm Owners’ Protection Act on 1986 wiped out some gun controls, it had a provision that banned the sale of machine guns to civilians (they are still produced for and sold to law enforcement). That law is still in place.

The only exception is gun collectors who want to buy old machine guns (generally very pricey); they must get a license from the Bureau of Alcohol, Tobacco, and Firearms, undergo a background check, pay a tax, and so on. Law enforcement near your residence even have to sign off on it. Machine guns cannot simply be bought with no questions asked. Perhaps it is then understandable semiautomatic assault rifles, so easily purchased, are a mass murderer’s best friend (whether modified or not).

Perhaps not surprisingly, from 1934-2010 there has only been one homicide involving a civilian with a licensed and registered machine gun (today there are just under half a million machine guns registered with the ATF, many belonging to law enforcement).

Illegal machine guns — those unregistered, unlicensed, illegally sold, stolen, brought in from other countries, etc. — were, predictably, more of a problem, but not enormous. Statistics are scant, but some include:

• From 1983-1992 in the U.S., 0.6% of police deaths involving civilians with guns involved machine guns.
• In 1980 in Miami (when homicides were peaking and the city was dubbed the “machine gun mecca”), less than 1% of homicides involved machine guns.
• From 1987-1989, the Minneapolis police recovered 2,200 guns, with zero machine guns.
• From 1980-1989, Chicago drug arrests yielded 375 guns, with zero machine guns.
• 0.7% of the guns taken by Detroit police from 1991-1992 were machine guns.

We must consider the implications here. Some of the most powerful guns are owned by very few people and are used in very few crimes. Why? Is it coincidence that a weapon that is so strictly regulated and quite rare, as it’s not mass produced, is rarely used in crime, while weapons that are loosely regulated and are mass produced are widely used?

Machine guns aren’t produced for civilians, so there is a limited supply; that limited supply is very hard to access — you must either steal one, illegally buy one, smuggle one in, or go through an extremely strenuous registration and licensing process, which you may not even pass if you have a criminal record or the FBI deems you suspicious. It is simply very difficult to get your hands on one — prohibitively difficult. And hence, you go with weapons easier to obtain (and/or modify), not to mention cheaper.

Making certain weapons (machine guns, bazookas, stinger missiles, grenade launchers, nukes, etc.) nearly impossible to get prevents their use. The old “gun bans don’t work” idea isn’t wholly accurate. They may not work perfectly (some machine guns will be stolen, some bought and sold on the black market), but they can work to an encouraging degree.

No, strict regulations and a halt of production didn’t stop all machine gun crime. No, semiautomatic assault rifles are not used in most crimes today. And no, the 1994-2004 assault weapons ban in the U.S. wasn’t as effective as some hoped, due to enormous loopholes that rendered it partly inert, and due to a lack of registration, licensing, and other machine-gun level regulations.

Yet if the measures the U.S. enacted to curb machine gun violence has made machine guns rare and difficult to get, and kept machine gun crime to a minimum, one might wonder if enacting the same sort of regulations on old semiautomatic assault rifles and banning new ones (and devices that turn them into fully automatic weapons) could work to reduce the number of casualties during mass shootings (or even the total number of mass shootings), perhaps saving some innocent lives.

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