What is a bump stock? The controversial gun attachment that allows for faster rate of fire

The Supreme Court's decision to strike down a Trump-era ban on bump stocks has put the issue back in people's minds.

Bump stocks are rapid-fire gun accessories that allow semiautomatic rifles to fire at a rate of hundreds of rounds a minute.

The ban was passed following the use of bump stocks in the deadly 2017 shooting in Las Vegas. Fifty-eight people were killed making it the deadliest mass shooting by one gunman in American history.

But the Supreme Court struck down the ban in a six-three decision. The conservative majority on the Supreme Court ruled that bump stocks are not machine guns.

Bump stocks are accessories that replace a rifle’s stock that gets pressed against the shoulder. 

A bump stock device (left) that fits on a semi-automatic rifle to increase the firing speed, making it similar to a fully automatic rifle, is installed on a AK-47 semi-automatic rifle, (right)

When a person fires a semi-automatic weapon fitted with a bump stock, it uses the gun’s recoil energy to rapidly and repeatedly bump the trigger against the shooter’s index finger. 

That allows the weapon to fire dozens of bullets in a matter of seconds.

The accessory allows a rifle to fire at nearly the rate of a machine gun without technically converting it into a fully automatic weapon - which are illegal.

Bump stocks were invented in the early 2000s after the expiration of a 1994 ban targeting assault weapons. 

The federal government approved the sale of bump stocks in 2010 after the Bureau of Alcohol, Tobacco and Firearms and Explosives concluded that guns equipped with the devices should not be considered illegal machine guns under federal law.

According to court documents, more than 520,000 bump stocks were in circulation by the time the Washington reversed course and imposed a ban that took effect in 2019. 

More than 22,000 people were attending a country music festival in Las Vegas on Oct. 1, 2017, when a gunman opened fire on the crowd from the window of his high-rise hotel room.

Authorities found an arsenal of 23 assault-style rifles in the shooter’s hotel room, including 14 weapons fitted with bump stocks. Investigators later concluded the gunman, who killed himself before police reached his room, fired more than 1,000 rounds in just 11 minutes.

In the aftermath of the shootings, the ATF reconsidered whether bump stocks could be sold and owned legally. With support from Trump, the agency in 2018 ordered a ban on the devices, arguing they turned rifles into illegal machine guns.

Bump stock owners were given until March 2019 to surrender or destroy them.

On Friday SCOTUS released its decision to lift the ban.

Justice Clarence Thomas wrote the opinion for the court. Conservative Justice Samuel Alito wrote a concurring opinion.

A bump fire stock that attaches to a semi-automatic rifle to increase the firing rate

Justice Sonia Sotomayor authored the dissent and was joined by Justices Elena Kagan and Ketanji Brown Jackson.

In the case Garland v Cargill, gun owner Michael Cargill surrendered two bump stocks to the ATF following the ban but then filed a lawsuit.

A district court ruled bump stocks are in line with machine guns, but the ruling was reversed by an appeals court.

'We hold that a semiautomatic rifle equipped with a bump stock is not a “machinegun” because it cannot fire more than one shot “by a single function of the trigger,”' Thomas wrote in the majority opinion.

The ban on bump stocks passed after the deadly shooting in Las Vegas in 2017. 58 people were killed and hundreds were wounded when a gunman opened fire on a country music festival

'And, even if it could, it would not do so “automatically.” ATF therefore exceeded its statutory authority by issuing a Rule that classifies bump stocks as machineguns,' he continued.

In his concurring opinion, Alito addressed the deadly shooting in Las Vegas where a man opened fire on a music festival from his suite at the Mandalay Bay hotel.

'The horrible shooting spree in Las Vegas in 2017 did not change the statutory text or its meaning. That event demonstrated that a semiautomatic rifle with a bump stock can have the same lethal effect as a machinegun, and it thus strengthened the case for amending §5845(b),' he wrote.

Justice Clarence Thomas (front row, second from left) wrote the majority opinion. Justice Samuel Alito (front row, second from right) wrote a concurring opinion. Justice Sotomayor (front row, far left) wrote the dissent 

'But an event that highlights the need to amend a law does not itself change the law’s meaning. There is a simple remedy for the disparate treatment of bump stocks and machineguns,' he went on.

He wrote that Congress can amend the law.

In her dissent, Justice Sonia Sotomayor wrote about the horrors of the shooting and how all the gunman using bump stocks affixed to semiautomatic rifles had to do was 'pull the trigger and press the gun forward. The bump stock did the rest.'

'Today, the Court puts bump stocks back in civilian hands,' Sotomayor wrote. 'To do so, it casts aside Congress's definition of "machinegun" and seizes upon one that is inconsistent with the ordinary meaning of the statutory text and unsupported by context or purpose.'

Sotomayor warned the Supreme Court's decision 'will have deadly consequences.