Two Kansas Republican members of Congress expressed support Thursday for a federal ban on over-the-counter accessories relied upon by the Las Vegas shooter to convert semi-automatic guns to fire at a rate mimicking automatic weapons.

U.S. Reps. Kevin Yoder and Lynn Jenkins said investigation into the killing or wounding of more than 550 people in Nevada demonstrated action ought to be taken to deter modification of semi-automatic rifles, such as an AR-15, with so-called bump-stock devices that enable people to sustain fire.

The Kansas branch of the National Rifle Association rejected the idea of blocking the sale of firearms add-on gear.

“Right now we have strict regulations on automatic weapons, but these devices allow an individual to easily convert legal firearms into an automatic weapon,” said Yoder, who serves the 3rd District in the Kansas City area. “That should not be the case. And, that’s why I will support measures to regulate or ban these types of devices.”

Jenkins, who represents the 2nd District that includes Topeka, said she remained a supporter of the Second Amendment right to bear arms, but was convinced “we should close the regulatory loophole that allows bump stocks and other devices like it.”

Federal officials investigating the massacre at an outdoor concert in Las Vegas indicated a dozen bump-fire stocks were recovered from shooter Stephen Paddock’s hotel room. The mass shooting Sunday night left 59 dead, including Paddock, and more than 500 injured.

The United States has restricted civilian purchase of fully automatic weapons since the 1930s, but not equipment amplifying firepower of weapons. Bump stocks are capable of increasing the firing rate to about 800 bullets per minute.

The National Rifle Association in Fairfax, Va., issued a statement endorsing regulation of devices that allow semi-automatic rifles to function like fully automatic weapons.

Moriah Day, chair of the Kansas State Rifle Association’s political action committee, said the state affiliate of the NRA was opposed to “any move to ban firearm accessories.”

“Accessory bans won’t save a single life,” Day said. “Prohibiting law-abiding gun owners from owning a piece of plastic won’t stop violent criminals. I find it absolutely despicable that the anti-gun lobby wants to place the responsibility for this violence on an inanimate object rather than the killer.”

Day said if Jenkins, Yoder or others in Congress wanted to save lives, they should support a federal law allowing national reciprocity of conceal-gun permits so owners of firearms could better defend themselves.

On Wednesday, U.S. Sen. Dianne Feinstein, D-Calif., introduced legislation that would ban the manufacture or possession of accessories that accelerate a semi-automatic rifle’s rate of fire to that of an automatic weapon.

“Why can’t we stop this?” Feinstein said. “Why can’t we keep a weapon from becoming a military battlefield weapon?”

On semi-automatic weapons, the trigger of the firearm must be pulled every time to fire a round. In that case, the weapon reloads itself. Automatic weapons are configured to continue firing for as long as the trigger is engaged or until the ammunition is expended.

Bump-fire stocks attach to the receiver of a rifle. The accessory enables a person to fire repeatedly because the recoil effect bounces the rifle off the shooter’s shoulder and into the individual’s trigger finger.