Assault rifle? AR-style rifle? Weapons in Orlando shooting spark language debate

• The semiautomatic AR-15 style rifle used in Orlando attack is a civilian version of military's M-16
• The weapons fire one round per finger pull and generally have 30-round magazines
• The nightclub shooter also carried a 9 mm semiautomatic pistol, ATF says

One of the weapons used in the Orlando nightclub tragedy is a type that's well-known and hotly debated, but even the terms used to describe it often become a point of contention in the wake of mass killings where it is used.

Traced to the shooting were a .223 caliber AR-type rifle and a 9 mm semiautomatic pistol, according to a Twitter post by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.

The shooting early Sunday morning at Pulse nightclub killed 49 people plus the shooter, and injured 53.

ATF spokesman Ali Berisha declined to elaborate on the agency's tweet, the weapons or any other aspect of the shooting Tuesday.

What is an AR-type rifle?

AR-type rifles originated with a weapon called an AR-15, which was developed by ArmaLite Rifles and later popularized by Colt. "AR" is short for ArmaLite Rifles.

Colt reconfigured the design and sold a military version as the fully automatic M-16. The semiautomatic civilian version is the AR-15, which retains the external look and feel of a military weapon.

RELATED: Study: For every gun used in self-defense, six more used in crime

The key difference is the military M-16 — and its shorter modern successor the M-4 — can be fully automatic, meaning they can discharge a full magazine of rounds with a single pull of the trigger. Civilian AR-15 style rifles shoot a single round per pull.

The high-powered rifles can reload quickly by swapping out spent magazines, which typically hold 30 rounds of ammunition. Defining elements to both the military and civilian versions are they are lightweight and use a pistol grip and trigger assemblies.

AR-15 style weapons are produced by dozens of gun manufacturers worldwide. Various makers use different names for their rifles, but AR-15 and the shorter AR have become the generic terms for modern lightweight semiautomatic pistol-grip rifles.

They are legal in all 50 states, provided the purchaser passes mandatory FBI background checks required for all retail gun purchasers, according to the National Shooting Sports Foundation, a pro-gun trade association.

Roberts: After Orlando, here's what will happen

Approximately 5 million to 10 million are legally owned in the United States, according to the foundation.

Some states have other restrictions on some of the weapon's features.

'Assault' rifle?

Debate continues about whether AR-15 style rifles should be considered "assault weapons" or "assault rifles."

The Shooting Sports Foundation, which calls them "modern sporting rifles," argues the guns don't meet the rapid-fire standard. "An assault rifle is fully automatic — a machine gun," the foundation states on its website.

"If someone calls an AR-15 style rifle an 'assault weapon,' he or she either supports banning these firearms or does not understand their function and sporting use, or both. Please correct them."

The legal standard for the terms vary by jurisdictions that enact laws using the terms.

Why is it popular?

By any label, the weapons have soared in popularity in recent years, according to a National Rifle Association blog entry entitled "Why the AR-15 is America's Most Popular Rifle," posted on Jan. 20.

"Spread the word on what AR really stands for, America's Rifle," it states.

Among the weapon's features: It's customizable, adaptable, reliable and accurate and can be used in sport shooting, hunting and self-defense situations, according to the post. They can be outfitted with a variety of stocks, barrels and sights.

Everything from the caliber of round to the colors and patterns on the stock can be changed.

"The AR-15's ability to be modified to your own personal taste is one of the things that make it so unique," the NRA states.

The AR-15 easily is the most common type of rifle sold at Caswells Shooting Range in Mesa, said Bridger Kimball, co-owner of Caswells Shooting Range.

"Here we did a 'Build your own AR-15' class where an instructor came in and your gun was in complete parts and he taught you how to build it from scratch. Those people who came into that class had the opportunity, the option, before class to order specific things to make their gun unique," Kimball said.

The rifle is modular, which makes customization fairly easy, he said.

"It's a super common and popular rifle. That's why you hear about them in shootings, I'm assuming, because it's a popular rifle," Kimball said.

The weapons also are versatile, according to the Shooting Sports Foundation. They're known for accuracy, reliability and ruggedness.

Depending on the manufacturer and features, AR-15 style guns sell for $500 to $2,500 apiece, Kimball said.

What other gun was used? 

While the ATF didn't name the manufacturer of the 9 mm handgun traced to the Orlando shooting, it showed a photo of a Glock in the Twitter post.

Those guns come in different varieties, but like AR-15 style rifles, they can be reloaded quickly by replacing spent magazines.

The Glock 17 is the most widely used law-enforcement pistol worldwide, according to the manufacturer. A standard magazine carries 17 rounds.

They sell for about $500, Kimball said.