WASHINGTON — If bump stocks need a defender in Congress after last week’s deadly massacre in Las Vegas, Rep. Thomas Massie is their man.

Bump stocks can be attached to a semi-automatic weapon to make it fire more rapidly, like a fully automatic weapon. And they’ve been under intense scrutiny since the Las Vegas killer reportedly used those devices in his Oct. 1 shooting rampage, which killed 58 people and injured hundreds more gathered for a country music concert

In the days since that incident—the worst mass shooting in modern U.S. history—Democrats have drafted a bill to ban bump stocks. Republicans have said they’re open to that idea. And even the National Rifle Association, a powerful gun lobby group, has suggested a federal review of the devices.

Massie, a Garrison Republican and self-described Class III firearms collector, has pushed back—hard. (Class III weapons include machine guns, short-barreled shotguns, and silencers, among other items.)

The chairman of the Congressional Second Amendment Caucus, Massie has long espoused staunch pro-gun positions. He has crusaded against the District of Columbia’s tough gun ban and tried to repeal the Gun-Free School Zones Act, which bars the possession and discharge of firearms near schools.

But since the Las Vegas shooting, Massie has taken his Second Amendment support to a new level, setting himself apart from his Republican colleagues and even the NRA.

The Kentucky congressman, who holds a concealed carry permit and says he is generally armed when he’s his home state, has questioned whether bump stocks truly made last week’s shooting in Las Vegas more deadly.

“Needs to be discussed: Murderer probably could have fired more rounds conventionally instead of dealing with misfires caused by #bumpstocks,” Massie tweeted on Oct. 7.

He has castigated his GOP colleagues for suggesting they would be willing to consider a ban on such equipment.

“Obamacare repeal and tax reform can't happen in 9 months, but now some GOP signaling they're ready to immediately work on gun control?” he blasted in another Twitter message.

The congressman even criticized a proposal issued last week by the NRA, which said the Bureau of Alcohol, Tobacco, Firearms, and Explosives should “immediately review whether these devices comply with federal law.”

That’s a “horrible idea” that would push the firearms agency to “contort existing law,” Massie told the Washington Examiner newspaper last week.

Massie’s spokeswoman said he was not available for an interview on Tuesday. But in his tweets and the Examiner interview, Massie suggested a new ATF rule could lead to restrictions on other firearms and accessories, such as high-capacity magazines. A legislative ban would similarly be a slippery slope, he has argued.

"There are at least a dozen ways to make a semi-automatic firearm more quickly," Massie told the Examiner. "There is no way to ban bump fire."

Not surprisingly, gun-control advocates vehemently disagree.

“We’ve regulated machine guns in this country quite carefully for the last 80 years,” said Avery W. Gardiner, co-president of the Brady Campaign to Prevent Gun Violence. “Why should an accessory that turns a gun into the functional equivalent of a machine gun not be regulated in the same way?”

She said Massie’s contention that such a ban cannot be written without ensnaring other legal firearms is absurd—and political cover for wanting to protect bump stocks.

“The idea that we aren’t clever enough to write a law that doesn’t address (those concerns) is a red herring,” Gardiner said. She noted that some states, including California and New York, have successfully restricted bump stocks.

She was left momentarily speechless when asked about Massie’s tweet suggesting that the Las Vegas murderer might have been able to fire more rounds with a conventional weapon because bump stocks cause so many misfires.

“I don’t have an answer as to whether the shooter used the most number of bullets he could have,” she said.

“What we know about the Las Vegas killer is that he had a lot of guns loaded and ready to fire upon the crowd of 22,000 people,” Gardiner added. “(And) I know that too many people were hurt. We need to take steps that are reasonable and consistent with the Second Amendment to reduce gun violence in America.”

A spokeswoman for the NRA declined to comment for this story. Massie has received $2,000 in campaign contributions from the NRA, and the group spent another $2,794 to boost his campaign, according to data compiled by the Center for Responsive Politics, a nonpartisan watchdog group. That’s a pittance compared to the NRA’s donations to other GOP lawmakers.

Michael Hammond, the legislative counsel for another gun-rights group, Gun Owners of America, called Massie an “interesting ally.”

“He thinks very deeply about these issues,” Hammond said. “He thinks beyond the surface questions. And incidentally on the bump stocks, he’s absolutely right.”

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