Discharging them at a gun range "is not target practice," she argued. "It is killing practice."

In Canada, the AR-15 is classified as a restricted, not prohibited, firearm. Its use is confined to a shooting range by a member of a gun club. Owners must complete extra licensing courses and are subject to screening by the RCMP before they are allowed to purchase and keep one.

Despite the heightened standards and precautions, Rathjen still believes "the risks are far too great and outweigh any benefits that these guns provide to a number of collectors or target shooters."

The AR-15 was wielded by terrorist Syed Farook during last year's San Bernardino attack in California, which claimed the lives of 14 people and left 22 seriously injured. Adam Lanza used a modified version to kill 20 children and six adults at Sandy Hook Elementary School in 2012.

Gun rights activists call the rifle a reliable, accurate and customizable sporting rifle for target shooting. Critics say it's a killing machine equipped with explosive firepower.

Silverdale chief range safety officer Gary Wilson said the public "likes to hate on firearm owners but we've done nothing wrong."

"If you have a restricted firearm, it's locked up in your house and when you want to use it, it has to be at an approved place," he said. "Basically, they are toys."

The retired Canadian Forces member wondered, "Why we are having conversations about tragic events elsewhere in the world when we have our own tragedies?" He cited as examples the plight of the country's homeless and mistreatment of First Nations people.

Canadian gun lobby groups emphasized that the AR-15 in Canada is used at a range by civilians for sport and friendly competition.

"There is no relationship between the criminal behaviour of a murderous terrorist and the activities of law-abiding firearms owners, shooting clubs and firearm businesses," Sheldon Clare, of the National Firearms Association, said in an emailed statement to the Star.

That sentiment was echoed by the Canadian Firearms Institute, a non-profit organization "dedicated to protecting Canadians' Firearms Heritage."

"The shooting in Orlando was a tragic event and our hearts go out to the families and victims," said Pyper Unitt. "The two issues are separate and distinct. One is an invitation to try a new sport — and the other a case of mental illness."

There has been no confirmation from official sources that Mateen was diagnosed with a mental illness.

ABOUT THE AR-15

The AR-15 is a lightweight, 5.56 mm calibre, air-cooled, gas-operated, magazine-fed rifle, with a rotating bolt, actuated by direct impingement gas operation. It is constructed of steel, aluminum and composite plastics.

Firing system

Many contemporary versions of the AR-15 utilize an operating system under the hood called direct-impingement. It relies on gas to move a bolt assembly that ejects the shell while triggering a spring that loads another bullet into the rifle chamber.

Trigger

To fire this semi-automatic firearm, the trigger must be released after each shot. Holding the trigger down does not mean it will rapidly fire.

Weight

Without a magazine, the AR-15 clocks in at 3.8 kg.

Customizable

Owners are able to personalize an AR-15 by changing its barrels, stocks and optics (such as adding a red dot sight instead of iron sights). Aftermarket parts are widely available.

Ammunition

Gun clubs like Silverdale load their AR-15s with FMJ, or full metal jacket, ammo. FMJ refers to the bullet's copper or steel alloy. This cuts back on lead residue left in the barrel after discharge and the bullets have less chance of fragmenting upon impact with soft tissue.

Rate of fire

According to one arms manufacturer, the weapon's effective rate of fire is 45 rounds per minute.

Toronto Star