According to the National Shooting Sports Foundation, a national trade organization for the weapon industry, nearly 20 million AR-15-style rifles are legally in circulation in the United States. Although AR-15-style rifles represent a small percentage of the country's roughly 400 million guns, their popularity has grown "exponentially" after the federal assault weapons ban expired in 2004, according to Mark Oliva, the NSSF's public affairs director.

In a report by ABC News, Brad Garrett, a news outlet contributor and former FBI agent, said that because AR-15-style rifles are so adaptable, with the ability to add scopes and adjust the length and diameter of the barrel, they've become a popular weapon among many Americans, particularly hunters.

Louis Klarevas, a research professor at Teachers College, Columbia University, who specializes in gun violence and safety told the news outlet that the use of these weapons in mass shootings is also on the rise. 

But, according to Garrett, the AR-15-style guns are also associated with patriotism among certain Americans, which may be traced back to the M16 military rifle that became popular during the Vietnam War.

Federal Assault Weapons Ban

Shootings in the 1980s culminated until President Bill Clinton in 1994 signed the Federal Assault Weapons Ban, stopping the manufacture, sale, transfer, and possession of these types of firearms. 

Cited by ABC, according to a report made by Klarevas in 2020, between 1984 and 1994, the United States saw a 43 percent drop in gun massacre deaths; while between 1994 and 2004, there was a 26 percent drop.

Congress did not renew the federal ban, as it expired in 2004. According to Klarevas' report, gun massacre incidents involving these weapons increased by 167 percent from 2004 to 2014, compared to the ten years the federal law was in effect. Active shooter incidents with various guns have been steadily increasing over the last two decades, according to FBI data, which do not break down murders by the exact model of gun used.

In the 1980s, assault rifles were used in less than 20% of gun massacres, but by the 2010s, that number had risen to 35%, according to Klarevas. His analysis says that these weapons were used in 67 percent of gun massacres in the last three years.

To ban or not ban 

According to an April study from Quinnipiac University, cited by the ABC news report, 27 percent of Republicans support an assault weapons ban and 70 percent reject it, while 88 percent of Democrats support the concept and 11 percent oppose it.

The study adds that 52 percent of Americans support and 43 percent oppose a nationwide ban on the sale of assault weapons.

While there is currently no federal assault weapons ban, Washington and seven states have passed laws prohibiting the possession of certain types of assault weapons, with the rules varying from state to state. Debate is still heated around the subject in the US.