US senators have announced an agreement on a bipartisan gun violence bill, marking a small but notable breakthrough on gun control in the wake of recent mass shootings.

Nine days after Senate bargainers agreed to a framework proposal – and 29 years after Congress last enacted major firearms curbs – senators Chris Murphy, a Democrat and John Cornyn, a Republican, told reporters on Tuesday that a final accord on the proposal’s details had been reached.

The legislation would toughen background checks for the youngest firearms buyers, require more sellers to conduct background checks and beef up penalties on gun traffickers. It would also disburse money to states and communities aimed at improving school safety and mental health initiatives.

The bill also contains provisions to curb domestic violence, including prohibiting romantic partners convicted of domestic violence and not married to their victim from getting firearms. And it would provide money to the 19 states and the District of Columbia that have “red flag” laws that make it easier to temporarily take firearms from people adjudged dangerous, and to other states that have violence prevention programs.

Lawmakers released the 80-page bill Tuesday evening. The measure is estimated to cost around $15bn, which Murphy said would be fully paid for.

The legislation lacks the far more potent proposals that Joe Biden supports and Democrats have pushed for years without success, such as banning assault-type weapons or raising the minimum age for buying them, prohibiting high-capacity magazines and requiring background checks for virtually all gun sales. Those measures were derailed by Republican opponents in an evenly divided Senate.

But the bill, if enacted, will still represent a modest but telling shift on an issue that has defied compromise since Bill Clinton was president. Congress prohibited assault-type firearms in 1993 in a ban that expired after a decade, lawmakers’ last sweeping legislation addressing gun violence.

Senators have seized on the momentum in the wake of devastating killings in Uvalde, Texas, and Buffalo, New York. Murphy said that after Buffalo and Uvalde: “I saw a level of fear on the faces of the parents and the children that I spoke to that I’ve never seen before.” He said his colleagues also encountered anxiety and fear among voters “not just for the safety of their children, but also a fear about the ability of government to rise to this moment and do something, and do something meaningful.”

This bill, Murphy said, was a partisan breakthrough that would “save thousands of lives.” Before entering the Senate, his House district included Newtown, Connecticut, where 20 children and six staff members perished in a 2012 mass shooting at Sandy Hook elementary school.

“Some think it goes too far, others think it doesn’t go far enough. And I get it. It’s the nature of compromise,” Cornyn said.

But he added, “I believe that the same people who are telling us to do something are sending us a clear message, to do what we can to keep our children and communities safe. I’m confident this legislation moves us in a positive direction.”

The Senate majority leader, Chuck Schumer, said his chamber would begin debating the measure right away and move to final passage “as quickly as possible”.

And in a positive sign about its fate, Senate minority leader Mitch McConnell voiced his support, calling it “a commonsense package of popular steps that will help make these horrifying incidents less likely while fully upholding the Second Amendment rights of law-abiding citizens.”

The National Rifle Association, which has spent decades derailing gun control legislation, said it opposed the measure. “It falls short at every level. It does little to truly address violent crime while opening the door to unnecessary burdens on the exercise of Second Amendment freedom by law-abiding gun owners,” the gun lobby group said.

The measure will need at least 10 Republican votes to reach the 60-vote threshold major bills often need in the 50-50 Senate. Ten Republican senators had joined with 10 Democrats in backing the framework, and Cornyn told reporters that “I think there will be at least” 10 GOP votes for the measure.

What’s uncertain is whether the agreement and its passage would mark the beginning of slow but gradual congressional action to curb gun violence, or the high water mark on the issue. Until Buffalo and Uvalde, a numbing parade of mass slayings – at sites including elementary and high schools, houses of worship, military facilities, bars and the Las Vegas Strip – have yielded only stalemate in Washington.

“Thirty years, murder after murder, suicide after suicide, mass shooting after mass shooting, Congress did nothing,” Murphy said. “This week we have a chance to break this 30-year period of silence with a bill that changes our laws in a way that will save thousands of lives.”

In powerful and emotional testimony about the sinister results of Donald Trump’s attempt to overturn the 2020 election, a mother and daughter who were Georgia elections workers described how Trump and his allies upended their lives, fueling harassment and racist threats by claiming they were involved in voter fraud.

Testifying to the January 6 committee in Washington, Shaye Moss said she received “a lot of threats. Wishing death upon me. Telling me that I’ll be in jail with my mother and saying things like, ‘Be glad it’s 2020 and not 1920.’”

That was a reference to lynching, the violent extra-judicial fate of thousands of Black men in the American south.

Moss also said her grandmother’s home had been threatened by Trump supporters seeking to make “citizen’s arrests” of the two poll workers.

No Democratic presidential candidate had won Georgia since 1992 but Joe Biden beat Trump by just under 12,000 votes, a result confirmed by recounts.

Tuesday’s hearing detailed Trump’s attempts to overturn that result via pressure on Republican state officials and vilification of Moss and her mother over video supposedly showing them engaged in voter fraud, a claim swiftly debunked.

Moss’s mother attended the hearing. In taped testimony, she said: “My name is Ruby Freeman. I’ve always believed it when God says that he’ll make your name great. But this is not the way it was supposed to be.”

“For my entire professional life, I was Lady Ruby. My community in Georgia, where I was born and lived my whole life, knew me as Lady Ruby. I built my own business around that name: Ruby’s Unique Treasures. A pop-up shop catering to ladies with unique fashions.”

“I wore a shirt that proudly proclaimed that I was and I am Lady Ruby. I had that shirt in every color. I wore that shirt on election day 2020. I haven’t worn it since and I’ll never wear it again.

“I won’t even introduce myself by my name anymore. I get nervous when I bump into someone I know in the grocery store who says my name. I’m worried about people listening. I get nervous when I have to give my name for food orders. I’m always concerned of who’s around me.

“I’ve lost my name and I’ve lost my reputation. I’ve lost my sense of security, all because a group of people starting with [Trump] and his ally Rudy Giuliani decided to scapegoat me and my daughter Shaye, to push their own lies about how the presidential election was stolen.”

Freeman also said: “There is nowhere I feel safe. Nowhere. Do you know how it feels to have the president of the United States target you?

“The president of the United States is supposed to represent every American. Not to target one. And he targeted me, Lady Ruby, a small business owner, a mother, a proud American citizen who stood up to help Fulton county run an election in the middle of the pandemic.”

Freeman said she had been forced to leave home for two months.

Moss described threats also made to her grandmother.

“That woman is my everything,” she said. “I’ve never even heard or seen her cry, ever in my life. And she called me screaming at the top of her lungs, like ‘Shaye, Shaye, oh my gosh, Shaye’, freaking me out, saying that people were at her home.”

“And they knocked on the door and of course she opened it, seeing who was there, who it was, and they just started pushing their way through, claiming they were coming in to make a citizen’s arrest. They needed to find me and my mom, they knew we were there.

“And [my grandmother] was just screaming and didn’t know what to do. I wasn’t there so I just felt so helpless and so horrible for her. And she just screamed and I called her to close the door. Don’t open the door for anyone.”

Moss was asked how her own life had been affected.

She said: “My life was turned upside down. I no longer give out my business card. Don’t want anyone knowing my name. Don’t want to go anywhere with my mom because she might yell my name out over the grocery aisle or something. I don’t go to the grocery store anymore.

“I haven’t been anywhere. I’ve gained about 60lb. I don’t want to go anywhere, I second-guess everything that I do. It’s affected my life in a major way, every way.

“All because of lies.”