WASHINGTON — The Senate Judiciary Committee approved a measure on Thursday to reinstate a ban on assault weapons, the first congressional vote on the issue since the ban expired in 2004.
The vote to approve the measure — now ostensibly headed for the full Senate — went firmly along party lines; the 10 Democrats on the committee voted yes, and the eight Republicans voted no. The legislation would also limit the size of ammunition magazines to 10 rounds.
In debating the measure — as well as amendments offered by Senator John Cornyn of Texas designed to chip away its provisions — the committee laid bare the essence and emotions of the debate over how to prevent gun violence and the meaning of the Second Amendment, a fight that is expected to continue on the Senate floor.
The measure, the fourth and most controversial passed by the committee, is almost certain to fail if brought before the entire Senate and has a minuscule chance of even receiving a hearing in the House.
“The road is uphill. I fully understand that,’’ said Senator Dianne Feinstein, Democrat of California and the sponsor of the bill, after its passage in the committee.
‘The road is uphill. . . . My passion comes from what I’ve seen on the streets,’ said Senator Dianne Feinstein, sponsor of the bill to ban assault weapons.
‘‘My passion comes from what I’ve seen on the streets,’’ she said, adding, ‘‘I cannot get out of my mind trying to find the pulse in someone and putting my fingers in a bullet hole.’’
Earlier this week, the panel passed a measure that would expand the use of background checks to private gun sales and another to renew a grant program to help schools improve security.
The committee also approved a measure last week that would make the already illegal practice of buying a gun for someone else who is legally barred from having one — known as a straw purchase — a felony and increase penalties for the crime.
The background check bill is expected to be substituted or amended by its sponsor, Senator Charles E. Schumer, Democrat of New York, to attract the support of more Republicans.
Cornyn offered amendments to the assault rifle bill to create exemptions. The measure would prohibit roughly 160 types of firearms from sale and use.
‘‘I respect your conviction,’’ he said to Feinstein, saying he would be inclined to vote for some sort of enhanced background-check bill although he rejected Schumer’s version Tuesday. ‘‘I hope we continue to work on that and improve it.’’
He rejected the assault weapons ban, he said, as it would jeopardize the ‘‘self-defense rights of law-abiding citizens.’’
His amendments, which would have allowed female victims of sexual assault, those who had received a protection order, and residents near the Southwest border to be exempt from the ban, all failed 8-10 along party lines.
The most testy exchange occurred between Feinstein and Senator Ted Cruz of Texas, who challenged Feinstein on her constitutional knowledge, asking her if she would apply regulations to the First and Fourth Amendments similar to those she’s seeking on firearm ownership.
Feinstein, who spent much of the hourlong hearing avoiding Cruz’s gaze, snapped, ‘‘I’m not a sixth-grader,’’ and added ‘‘Just know I’ve been here a long time.’’
The debate over who may obtain weapons, what type, and within what limitations goes to the heart of the interpretation of both the Second Amendment and the Supreme Court’s most recent findings on its limitations, which it found existed, without outlining what those specific limitations should be.
In a separate development, New York state officials said an overwhelming majority of gun show operators in the state have agreed to new rules to ensure that criminal and mental health background checks are conducted on buyers.
The agreement was reached after undercover agents from the attorney general’s office were able to buy weapons, including three semi-automatic rifles, without any screening at half a dozen gun shows around the state.
The investigators, posing as buyers, were able to purchase firearms even after they told the sellers that they had orders of protection against them, in which case they would fail background checks.
The operators, with shows from White Plains to Cheektowaga, have also agreed to a broader system to track firearms at their shows and to guard against illegal sales in parking lots.
The agreement was negotiated by Attorney General Eric T. Schneiderman, who had brought criminal charges against the sellers identified in the sting operation.
New York law has required universal background checks for guns sales since 2000, but Schneiderman said there was ample evidence they were not being followed.
''Our goal is to have 100 percent of the gun show operators on board, and then we have a good example for other states to follow,’’ Schneiderman, a Democrat, said this week. ‘‘Once we demonstrate how easy this is and how it keeps people safe, it weakens the arguments on the federal level that guaranteeing background checks are overly burdensome or face meaningful opposition.’’
The 23 operators who have agreed to the protocols are responsible for about 80 percent of gun show sales in the state.