Corrections and Clarifications: A previous version of this story erroneously included a mass shooting in Oregon in which the gunman did not use an AR-15.

AR-15 style rifles have been the weapon of choice in many recent mass shootings, including the Texas church shooting Sunday, the Las Vegas concert last month, the Orlando nightclub last year and Sandy Hook Elementary School in 2012.

The manufacture of rifles more than doubled in the past decade, to nearly 3.7 million rifles manufactured in 2015, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Much of the growth coincided with the Obama administration, when industry experts said gun owners were worried the government would restrict weapon sales.

Amid that growth, the AR-15 style weapon became popular for its ease of use and versatility. The National Rifle Association has called the AR-15 the "most popular rifle in America" and estimates Americans own more than 8 million of them.

The NRA said "the AR-15 has soared in popularity" because it's "customizable, adaptable, reliable and accurate." It is also versatile and can be used for "sport shooting, hunting and self-defense situations," the NRA said, adding the ability to "personalize" so many of the rifle's components "is one of the things that makes it so unique."

The site TacticalGear.com offered a favorable comparison of the U.S. AR-15 to the Russian-made AK-47. The AR-15 has a higher base price, shoots farther effectively, fires more rounds per minute, is lighter and its service life is longer if properly maintained, the site said.

The Brady Campaign to Prevent Gun Violence said the AR-15, a civilian model of the military’s M-16, also cited the weapon’s versatility in evaluating its popularity.

“They’re accurate and they can basically shoot as quickly as you can pull the trigger,” according to a campaign statement. “Along those lines, they’re very customizable — most average people can figure out how to install accessories like forward trigger grips that let you hold the gun at waist height and spray bullets while stabilizing the gun, laser sights, and you can add high-capacity magazines.”

Dean Hazen, owner of The Gun Experts in Mahomet, Ill., and a master firearms instructor, said the reason mass shooters are turning to the AR-15 is due to a "copy-cat" mentality more than any feature of the rifle.

"It’s really just a perception thing," Hazen said. "There are rifles that are more powerful and more dangerous than that, but they're not being used."

For example, Hazen says the AK-47 — and its semiautomatic variants — is a "far more wicked gun than an AR-15." The AK-47 variants can hold just as many rounds as the AR-15, are more reliable and use larger 7.62 mm rounds as opposed to the standard AR-15's .223 rounds.

Some killers might be drawn to the AR-15 because they are the "weapon of choice" for the military and police. But ironically, the police "choose it because it is under-powered, Hazen said, "making it less likely to penetrate interior walls and hit an unintended target." The Army is considering moving to a higher-caliber rifle partly because that would make the weapon more deadly.

Hazen said the AR-15 has "gotten a bad rap." He believes mass shooters generally don't know much about guns and choose the AR-15 because of the reputation it has gotten from being used in other mass shootings.

"Thank God they don't know any better because if they did they would use much more effective weapons," Hazen said.

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Youngest Texas shooting victim just 18 months old: What we know now

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Here is a list of mass shootings in the U.S. that featured AR-15-style rifles during the last 35 years, courtesy of the Stanford Geospatial Center and Stanford Libraries and USA TODAY research: