SPRINGFIELD — Illinois House Democrats have endorsed banning firepower-boosting "bump stocks," the same device used by the Las Vegas gunman in the nation's deadliest mass shooting three weeks ago.

The Judiciary Committee's 7-5 tally along party lines signals a floor vote involving a device few people had even heard of before 58 people died Oct. 1 in the Nevada massacre.

Only one other state — Massachusetts — has thus far taken up bump-stock restrictions.

"It's a device used to kill and injure as many people as you can by modifying a semi-automatic weapon into an automatic weapon," the legislation's sponsor, Democratic Rep. Marin Moylan of Des Plaines, told the committee on Tuesday.

Critics call it an overreach because Moylan's measure technically addresses "trigger modification." It's defined in part as any implement "intended to accelerate the rate of fire of a firearm."

Sport-shooters routinely make after-market modifications to get an edge on firing speed, the National Rifle Association's Todd Vandermyde testified. He labeled Moylan's language so broad, "it would make a criminal out of the vast majority of the state's 2.2 million" Illinois firearm-permit holders.

Bump stocks were found on 12 of the rifles stockpiled by the Las Vegas gunman. Bump stocks don't affect the trigger but allow more rapid firing by relying on the inertia of the recoil to simulate a rapid-fire weapon.

The NRA has endorsed the request by nine Republican U.S. senators for federal authorities to review bump stocks' capacity for harm. A U.S. Senate bill would ban them nationally but appears stalled, said Avery Gardiner, co-president of Brady Campaign to Prevent Gun Violence.

California explicitly bans bump stocks and New York restricts weapons that "simulate machine guns," Gardiner said. Minnesota, Michigan, New Jersey and Oregon have laws restricting devices that accelerate firing rate. And seven states and the District of Columbia have assault-weapons bans.

Gardiner said, however, that the answer is on Capitol Hill, not in patchwork state laws.

"They're important, they're effective, they're good," Gardiner said. "But without a federal standard, there's the opportunity for people to take advantage of weaker laws in neighboring states and import them, thereby endangering Illinois."

The Illinois State Rifle Association opposes Moylan's proposal, too, citing the restriction on law-abiding sport-shooters. But it differs from the NRA on bump stocks.

"They're used by bad people," Illinois State Rifle Association lobbyist Ed Sullivan told the committee. "But the unintended consequences of this bill are that it prohibits altering a trigger to advance the rate of speed."