Rep. Thomas Massie, the libertarian-leaning Kentucky Republican who leads the Congressional Second Amendment Caucus, has been one of the few legislators to openly resist demands for a ban on bump stocks, the devices that Stephen Paddock reportedly used in his October 1 attack on a country music festival in Las Vegas. In a telephone interview today, Massie detailed his objections, which are practical as well as philosophical.

1. It is not clear that bump stocks increased the death toll in Las Vegas.

"It's an assumption based on a lack of facts right now," Massie says. Judging from audio of the attack, he says, "It's my guess that the shooter had a bona fide machine gun in the first volley of rounds that he fired at the crowd, and it's my guess that subsequent volleys were fired with a bump stock. You can hear the difference."

Massie, who owns several registered (and strictly regulated) machine guns as well as semiautomatic weapons that he has been shooting for two or three decades, notes that bump fire, which involves bouncing the trigger against a rigid finger, is notoriously inaccurate and prone to misfiring. A bump stock, he says, is basically "a horizontal pogo stick" that "makes your weapon less accurate and more likely to jam."

A misfire can happen when "the weapon doesn't move far enough [back] to engage the trigger," when "you hold the trigger too tight so that you never really disengage the trigger before the firearm cycles," or when "you engage the trigger too quickly, and the bolt has not closed on the shell yet." Massie says bump-fired weapons may also be more vulnerable to stovepiping, a malfunction caused by an incompletely ejected casing.

"If you spent 12 minutes firing a semiautomatic weapon without jams, you could discharge far more rounds than [Paddock] discharged," Massie says. "I'm going to go out on a limb and maintain that this guy's fetish with bump stocks caused him to kill fewer people, not more, that his firearms were jamming, that they were inaccurate, and that many of his rounds did not go where he intended. If he had been more clear-thinking and methodical about it, he could have inflicted more casualties by shooting his firearms without bump stocks."

2. Banning bump stocks will have no impact on the frequency or lethality of mass shootings.

Given the limitations of bump stocks, Massie says, a ban "will have zero effect." Previous mass shooters have not needed them to kill dozens of people, and there is no reason to think future mass shooters will be deterred if the government takes bump stocks and similar accessories off the market.

3. Banning bump stocks creates a slippery slope.

"If what you have a problem with is the lethality of the firearms that [Paddock] took into that room," Massie observes, "then really what you're going to go after is semiautomatic firearms with detachable magazines and higher-caliber weapons and scopes and tripods, all of which do more to enhance lethality than a gimmicky bump stock." At that point the legislation would affect core Second Amendment rights.

4. Restricting bump stocks through administrative action would undermine the rule of law and the separation of powers.

Some of Massie's colleagues, joined by the National Rifle Association, have urged the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) to reconsider its determination that bump stocks do not convert semiautomatics weapons into machine guns. But that conclusion was based on a straightforward application of the National Firearms Act.

"The law defines a machine gun as a firearm that can discharge more than one round with a single pull of the trigger," Massie notes. "If you look at how bump fire operates, you are pulling the firearm against your trigger finger, thereby discharging the weapon, and each and every time the weapon discharges, your finger is engaging the trigger."

The proposed bump stock ban that was introduced today, which applies to "any part or combination of parts that is designed and functions to increase the rate of fire of a semiautomatic rifle but does not convert the semiautomatic rifle into a machinegun," implicitly concedes that the ATF was right about the legal status of these products. Reversing that determination therefore would require rewriting the law.

"You have some congressmen right now who are asking the ATF to pervert the language of the law to ban bump-fire-enabling stocks," Massie says. "It is the height of legislative malpractice to ask the executive branch to legislate….[It's] an abdication of our legislative responsibility. We're asking the ATF and the president to do our job."

The NRA says it opposes new legislation but wants the ATF to re-examine the legality of bump stocks. "The NRA is generally pretty good at defending our Second Amendment, so I don't want to question their motives," Massie says. "I think it's a well-intended but ill-advised strategy to keep this out of the political realm and to save members of Congress from having to weigh in on this. But it will come back to bite us, and it erodes the system of government that the Founding Fathers intended to set up."

Having said all that, Massie suggests that the push for a ban on bump stocks might present an opportunity to accomplish something constructive. "What about a trade?" he says. "Some Second Amendments proponents have said, 'These bump stocks are a gimmick, but some people are upset about them. Let's offer to regulate the heck out of them in exchange for unregulating the heck out of sound suppressors.'"

Suppressors, a.k.a. silencers, provide a measure of hearing protection by reducing the noise of gunfire (although guns equipped with them are still plenty noisy, contrary to what Hillary Clinton seems to think). Suppressors are currently regulated as strictly as machine guns, for reasons that do not make much sense, and the NRA backs a bill that would loosen those restrictions. "I wouldn't dismiss that idea [of a trade] out of hand," Massie says, "because you would be satiating the emotional need to feel like you've done something to prevent one of these [attacks], whether or not it does, while at the same time expanding the scope of our freedom and protection of the Second Amendment."