The 35-page bill (S 2572) clocks in at 94 pages fewer than the controversial gun bill the House approved in October (H 4139), though it takes aim at many similar topics.

Senate Majority Leader Cynthia Creem, the bill’s chief architect, said the legislation would rein in the spread of ghost guns by requiring serialization of gun frames and receivers and by classifying those individual parts as firearms. It would also explicitly prohibit the use of 3D printers to manufacture or assemble firearms without a license.

“Massachusetts gun laws are currently inadequate at preventing the unlawful possession of guns, and particularly the growing phenomenon of untraceable ghost guns,” Creem said. “This bill will track these unlicensed weapons the same as any other gun and keep them out of the hands of people who are not licensed to carry.”

The bill would expand the state’s “red flag” law, which allows individuals to petition a court to remove someone’s ability to possess guns if they are deemed dangerous, by allowing health care providers to seek those extreme risk protection orders. Unlike the House bill, however, the Senate version would not extend that power to school administrators or an individual’s employer.

In another area of partial overlap, the Senate bill prohibits carrying firearms in government administrative buildings, including courthouses. It does not mirror the House’s proposed ban on bringing guns into schools, polling places or private residences where the owner has not given consent.

Creem said existing state law already bans possession of firearms in schools, “so we didn’t need to redo what was done.”

The Senate bill would also allow individual municipalities the ability to opt out and grant licensed gun owners the ability to carry in local government buildings.

Another change senators made would seek to give firearms licensing agencies up-to-date information about applicants who have been involuntarily hospitalized for mental health reasons.

Creem said the bill would “hold the gun industry accountable for marketing” by banning the marketing of unlawful firearm sales to minors. People harmed “as a result of such unlawful advertising” could pursue civil action, she said.

The legislation bans possession of devices that make semiautomatic weapons fire more quickly, sometimes known as Glock switches or selector switches.

“We now, unlike five or 10 years ago, respond to crime scenes where it is not unusual to find that over 100 shots have been fired, sometimes in less than 10 seconds,” said Middlesex District Attorney Marian Ryan, who joined senators and police chiefs at the bill unveiling. “Those bullets go somewhere. They often go into people’s homes, they go into cars, and sometimes they hit innocent bystanders.”

Additional parts of the bill would require people who are subject to harassment prevention orders and deemed to pose a threat to surrender their firearms; work to ensure dealers are inspected every year; codify the state’s assault weapons ban; create a new criminal charge for firing a weapon at an occupied building or home; and expand data collection efforts.

Unlike their counterparts in the House, senators will embark on debate with the Massachusetts Chiefs of Police Association on their side from the outset.

MCOPA members unanimously voted not to support the House bill shortly before representatives approved it, warning that its proposals to overhaul firearm registration and limit where guns can be carried “will not reduce gun violence.”

But the association representing hundreds of law enforcement officials gave a clear endorsement of the Senate bill, with its top leader, Agawam Police Chief Eric Gillis, joining Senate Democrats at a press conference to unveil the measure.

Gillis said his group was won over by “all the conversations, the ability to collaborate with Senate leadership about how a bill should be crafted, what would be effective, what wouldn’t be effective.” He declined to highlight any specific policies that MCOPA prefers in the Senate version to the House version.

“I don’t think we’re going to get into a back and forth and contrast about what we like in the Senate bill versus what we have issue with in the House bill,” Gillis said. “I can say that what we find in the Senate bill makes sense. It’s concise. At the end of the day, it has to be enforceable. Whatever this body does has to be carried out by people in our sphere, and when it’s distilled down and simple and makes sense, it’s going to work. So that’s what works for us.”

Gun owners and Second Amendment groups vocally opposed the House’s efforts last year to update the state’s gun laws, pitching it as government overreach. Jim Wallace, executive director of the Gun Owners’ Action League, said Thursday afternoon that he was still reviewing the Senate’s proposal.

“It looks like we were the only ones who weren’t given a preview before the release,” he said.

In 2021, the most recent year with Centers for Disease Control data available, Massachusetts experienced 3.4 firearms deaths per 100,000 residents, the lowest of any state in the nation. Democrats in both chambers have called for significant action this term to maintain the Bay State’s national position, particularly as ghost guns become more common.

Ryan said that in Cambridge and Somerville alone, there have been more than 20 shootings involving ghost guns and young people over the past year.

Gun violence also disproportionately impacts lower-income communities and people of color.

“Our state, I think all of you know, has one of the lowest rates of gun violence in the nation, and this fact is not by accident,” Senate President Karen Spilka said. “It’s because we have been vigilant in updating our gun safety laws, our gun laws, to prevent those who wish to do harm from being able to access and use deadly weapons.”

While legislative leaders in both the House and Senate have expressed a desire to send Gov. Maura Healey a gun reform bill, they spent much of last year publicly sparring over the process they should use.

The House eventually muscled its bill to the floor without any joint committee involvement before approving it 120-38.

Senators never referred that bill to a committee for official review, a departure from the normal pattern in which the Senate Ways and Means Committee tees matters up for floor action. Instead, the measure they outlined Thursday will advance as an amendment Creem filed striking and replacing the entire text of the House bill.

Amendments to the Senate bill are due by 5 p.m. Monday, and Senate Democrats plan to bring the bill forward for a vote on Thursday, Feb. 1.