Twenty first-graders and six educators in a school in Connecticut. Twelve people watching a movie at a theatre in Colorado. Nine people at a college in Oregon. Fourteen county employees at a Christmas party in San Bernardino, Calif.

And 49 people at a gay nightclub in Orlando, Fla.

What do all these people — sisters, brothers, mothers, fathers and friends — have in common?

They were shot dead with an increasingly popular breed of assault-style weapon that has become the weapon of choice for killers bent on taking as many human lives as possible.

In Orlando, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives and the city's police department have said the shooter used an "AR-type rifle," referring to the ArmaLite-15, more commonly known as simply the AR-15. 

However, several media outlets are reporting, based on unnamed police sources, that the weapon used at the nightclub was, in fact, a Sig Sauer MCX — a high-power rifle similar in form and function to the AR-15.

Regardless of which specific model of assault rifle was used in the Orlando shooting, there is little doubt that incredibly fatal semi-automatic guns like the AR-15 and the Sig Sauer MCX are at the heart of the ongoing battle over gun control in the United States.

Gun-control advocates want to bring back the assault rifle ban signed under U.S. President Bill Clinton in 1994, which prohibited civilian use of certain high-powered guns the government classified as assault weapons, as well as "large-capacity magazines," though that definition varied.  

But for gun advocates, that would be a violation of the individual liberty that many U.S. citizens hold dear. Besides, they argue, there are many deadly weapons that the ban wouldn't cover, so what's the difference? 

The AR-15, the weapon of choice in many of the most recent high-profile mass shootings in the U.S.,  is revered for its ability to fire rounds as quickly as the shooter can pull the trigger. It's light (about three kilograms fully loaded), versatile, loads quickly and is accurate up to 500 yards (about 460 metres) and highly customizable.

Gun makers know their market

The existence of the AR-15 dates back to the 1950s. Today, more than 200 companies manufacture their own version of the rifle. 

"Gun makers' target market is young men, and they've certainly figured out that young men tend to buy these kinds of weapons. So, they market to them relentlessly," said Josh Sugarmann, executive director of the Violence Policy Center in Washington, D.C.

Assault rifle

Gun enthusiasts look over Sig Sauers guns at the National Rifle Association's 2016 annual meeting and exhibits show in May. Some media have reported that it was a Sig Sauer rifle that was used to carry out the mass shooting in Orlando. (John Sommers/Reuters)

There's also a huge after-market for gun manufacturers, with all kinds of expensive options for customizing the rifle.

The National Rifle Association (NRA) has almost made an art out of advertising all the different ways you can upgrade an AR-15. 

A powerful symbol

AR-15-type rifles have become extremely popular in the U.S. since Clinton's decade-long ban ended in 2004. While it's difficult to pin down a precise number, there are at least three million of these kind of rifles in circulation, but some estimates say that figure could be as high as five million. 

The AR-15 is, in effect, a battlefield gun, according to Ladd Everitt, spokesman for the Coalition to Stop Gun Violence, a non-profit, anti-gun organization based in Washington, D.C. 

AR-15

Three variations of the AR-15 assault rifle are displayed. They look similar, but modifications mean each one is equipped for different situations. (Rich Pedronelli/AP)

While, proportionally speaking, AR-15s are involved in a very small number of homicides, they have become the weapon of choice for mass shooters, many of whom are young men. 

Hard-core Second Amendment supporters use AR-15-type rifles as a symbol of liberty while those who support stricter gun laws hold it up as an icon of gun policy gone wrong and proof the ban on some semi-automatic and automatic weapons should be reinstated. 

'Gun makers target market is young men, and they've certainly figured out that young men tend to buy these kinds of weapons.'
- Josh Sugarmann, executive director of the Violence Policy Center  

Everitt says people who don't live in the U.S. and are not familiar with the country's gun culture don't understand how deep the symbolism of the AR-15 runs.

Over time, it has come to represent the ultimate form of resistance for some, Everitt said.

'Poster boy' for gun control

Of course, most law-abiding U.S. gun owners use AR-15 type rifles to hunt or at the gun range.

They're also available in Canada but can only be fired for target practice and in sanctioned competitions. The magazine is limited to five bullets. 

Newfoundlander Marc Bennett has managed to gather more than 25,000 signatures on an e-petition calling on the government to make AR-15 type rifles legal for hunting in Canada. He said he has been watching the situation in the U.S. very closely. 

AR-15

Sales of the AR-15 and similar rifles went up after the mass shooting in Newtown, Conn., in 2012 that left 20 children dead. Gun owners were concerned there might be a new ban on semi-automatic rifles. (Alex Brandon/AP)

He says weapons like the AR-15 and their variants are being used to scare people and build support for the gun-control lobby.

"It's just the look of it. It's no different than any other rifle with wood on it," Bennett said. "It's black, it's intimidating. So, these politicians who want to keep pushing gun control further and further are going to put it up as a poster boy for their agenda, because you can't scare people with a regular old shotgun that maybe their granddad had growing up."

Bigger gun problem

Joseph Blocher, a law professor at Duke University in North Carolina says he supports "sensible" gun control but agrees that weapons like the AR-15 hold "a disproportionate weight in our discussions about gun laws."

"These semi-auto assault-type guns are in the news, and I think most people thought they'd be banned after Sandy Hook, but it can't just be about the assault rifle ban," he said. "There's a slow drip of daily handgun deaths in cities around the country every day, and we need to address that, too."

Multiple gun policy experts CBC interviewed for this story expressed doubt that last weekend's massacre at Pulse nightclub in Orlando, the deadliest mass killing by a single shooter in U.S. history, will have any major influence on gun laws in the U.S. The NRA is among the most powerful lobbies in Washington, and right now, assault rifles like the AR-15 are gun makers' bread and butter.  

But, as Sugarmann points out, "people get a glimpse of the real gun industry when horrific events like this happen, and maybe now, things will move in the right direction a little bit."

Corrections

  • A previous version of this story said an AR-15 rifle was used in the deadly Orlando shooting. In fact, authorities have not confirmed the exact model of weapon used but have said it was an "AR-type rifle."
    Jun 14, 2016 10:45 AM ET
  • A previous version of this story mistakenly attributed direct quotes to Ladd Everitt that were not verbatim. The story has been changed to reflect that.
    Jun 16, 2016 6:27 PM ET