Following reports of a .50 caliber sniper rifle attack on U.S. Border Patrol agents, Fox News hosts immediately recognized the threat the high-powered “battlefield weapon” poses to law enforcement. Criticism of the gun on Fox, however, stands in sharp contrast to the National Rifle Association's longstanding campaign to prevent the regulation of .50 caliber weapons, which are manufactured by one of its board members.

On July 20, FoxNews.com reported that U.S. Border Patrol agents working near the Rio Grande River came under fire from a .50 caliber weapon during the evening of July 18. According to the report, “Border Patrol sources said the rounds were clearly identifiable because .50- caliber weapons make a distinctive noise when fired.” No agents were wounded in the attack.

In most of the United States the .50 caliber sniper rifle is regulated no more strenuously than a typical hunting rifle, thanks to efforts by the gun lobby. But Fox News personalities covering the border incident were quick to recognize the rifle's extremely dangerous capabilities and the threat it poses to law enforcement.

Fox News host Heather Nauert opened the July 20 edition of Fox & Friends Sunday by citing the .50 caliber rifle incident as evidence that “there is an all-out war on at our southern border.” Throughout the show, Nauert's co-hosts repeatedly returned to the capabilities of the .50 caliber rifle. Fox's Jon Scott described the rifle as “a weapon of war,” noted that, “The slugs a .50 caliber weapon fires are so big that body armor really won't do you much good,” and called it a “battlefield weapon.”

The weapon's capabilities continued to be a topic of conversation of the July 21 edition of Fox & Friends, with co-host Steve Doocy pointing out the gun is “powerful enough to kill somebody from more than a mile away.” Co-host and Fox News legal analyst Peter Johnson Jr. described it as “multiple times the power of an M-16,” a reference to the standard issue military assault rifle.

All of the claims made by Fox figures about the rifle's capabilities are accurate -- the gun has been characterized by a retired high-ranking federal law enforcement agent as “a devastatingly powerful weapon against which most troops, most law enforcement, no civilians, have any means of defense.” But while .50 caliber rifles have previously fallen into the hands of terrorists, anti-government extremists, and Mexican drug cartels, the class of weapon is generally not subject to heightened regulation in the United States.

There is no federal law that specifically regulates .50 caliber rifles, meaning they can be purchased by anyone aged 18 or older who passes a background check at a licensed gun dealer (and in 33 states the rifle can be bought without a background check through the private sale loophole). California and the District of Columbia ban the .50 caliber sniper rifle, while Connecticut and Maryland put some restrictions on its ownership.

The NRA has long opposed the regulation of .50 caliber rifles and in 2013 the gun organization successfully urged Republican New Jersey Governor Chris Christie to veto a .50 caliber rifle ban. The NRA also lobbied against a 2005 U.S. House of Representatives bill to restrict .50 caliber rifle ownership -- which it misleadingly labeled as a “hunting rifle ban” -- and opposed .50 caliber state regulation efforts in California and Hawaii.

The NRA has a financial interest in promoting access to the .50 caliber rifle. The inventor of the .50 caliber rifle, Ronnie Barrett, sits on the NRA board of directors. Barrett has maintained a close relationship with the NRA, and his company has donated between $50,000 and $99,000 to the gun group. In 2010 the NRA bestowed Barrett with an award that recognized “exemplary achievement by individuals who were responsible for the development, introduction, and promotion of equipment that has made a profound and enduring impact on the way Americans shoot and hunt.”

Fox repeatedly used a photograph of a Barrett .50 caliber rifle to illustrate its reports on the border shooting.

The NRA is a fierce defender of attempts to regulate Barrett's product, falsely arguing that .50 caliber weapons pose no threat to the general public. An August 16, 2013 press release issued by the NRA's lobbying wing, the Institute for Legislative Action, praised Christie's .50 caliber rifle veto, writing, “The NRA argued in public testimony that these firearms are used by competitive shooters and collectors, and are not misused in crime. Governor Christie agreed.” Other material from the NRA-ILA has claimed, ".50 caliber rifles are not used in crimes--.50 caliber rifles are too large and heavy to be employed in normal criminal behavior," and attacked critics of the .50 caliber sniper rifle as engaging in “phony terrorism hype.”

Gunfire at the U.S. border is the latest incident disproving the false claims the NRA makes to keep .50 caliber rifles legal. Gun violence prevention group Violence Policy Center has documented myriad serious crimes involving the .50 caliber rifle including assassinations of law enforcement agents and use by anti-government militias and other extremists.

Media Matters intern Karley Jarin contributed to this blog.