With support building in Congress for action against devices like those the Las Vegas gunman had, which allow a rifle to fire hundreds of rounds per minute, the National Rifle Association on Thursday endorsed tighter restrictions on the gadgets, but did not say they should be outlawed.

The stance by the NRA, and growing support for regulation from Republicans on Capitol Hill, represent a small but notable shift for an organization and political party that have consistently opposed any gun controls for many years.

Stephen Paddock, the man who took aim Sunday night from a 32nd-floor hotel suite into the crowd at a music festival, killing 58 people and wounding hundreds of others, had 23 firearms with him, including 12 equipped with “bump stocks,” one type of device that can turn a gun into a rapid-fire weapon, shooting bullets at a rate comparable to a machine gun.

The Bureau of Alcohol, Tobacco, Firearms and Explosives has said that the apparatus does not violate federal laws that, since the 1930s, have sharply limited the manufacture and possession of fully automatic weapons, or machine guns. In a statement on Thursday, the NRA said the bureau should revisit the issue and “immediately review whether these devices comply with federal law.”

“The NRA believes that devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations,” the group said.

Last year, the NRA’s online magazine, America’s First Freedom, called one of the rapid-fire devices “sublime,” and advised users to keep copies of the firearms bureau’s ruling that such items are legal.

Sales of bump stocks surged this week after news emerged that they might have been used in the Las Vegas shooting. Some retailers ran out of the devices, even as others decided to stop offering them on their websites.

Democrats have supported legislation banning such mechanisms, particularly a bill introduced in 2013 by Sen. Dianne Feinstein of California, while Republicans generally have not. But since the massacre, several leading Republicans, including Sen. John Cornyn of Texas, the No. 2 Republican in the Senate, have raised serious questions about the devices.

In the House, Rep. Carlos Curbelo, R-Fla., has drafted a measure banning bump stocks, and he said on Thursday that his office has been flooded with calls from “dozens” of his fellow Republicans, who want to sign on.

“I think we are on the verge of a breakthrough when it comes to sensible gun policy,” Curbelo said.

His comments followed those of House Speaker Paul Ryan, R-Wis., who during a morning interview with MSNBC also raised questions about the conversions, and said he was open to legislation. “Clearly that’s something we need to look into,” Ryan said.

Separately, Rep. Adam Kinzinger, R-Ill., is circulating a letter among his colleagues, calling on the ATF to re-evaluate bump stocks, which he said have “no place in civilized society.”

“The ATF must re-evaluate these devices,” Kinzinger wrote, “and it is my hope that they conclude these mechanisms violate the spirit, if not the letter, of the law.”

But gun control advocates drew a sharp distinction between a ban, like that proposed by Feinstein, and merely asking the firearms agency to re-evaluate the matter, as the NRA and Kinzinger have.

“If they had actually said we support bipartisan legislation, you might have characterized it as a concession,” said John Feinblatt, president of Everytown for Gun Safety. “But they’re actually just punting it back to the very federal agency that said bump stocks were legal. I don’t think this is a concession, it’s just a wink and a nod.”

In its statement, the NRA also urged Congress to pass one of the group’s highest legislative priorities, a bill that would allow anyone who is licensed by one state to carry a concealed weapon to do so in any other state that allows concealed carry.

Sen. Richard Blumenthal, D-Conn., accused the NRA of pursuing “a road to nonaction.” He noted that a regulation — as opposed to a law — could take years to enact, and that Democrats have opposed the reciprocity measure.

“I think it’s a highly dangerous and deceptive dodge,” Blumenthal, who is co-sponsoring legislation to ban bump stocks, said in an interview. “It’s typical NRA evasion and avoidance of reality; the simple, stark political fact is there is growing support for a ban, a complete prohibition.”