WASHINGTON — During a lengthy and at times emotionally wrenching news conference, Senator Dianne Feinstein announced legislation Thursday that would ban the sale and manufacture of 157 types of semiautomatic weapons, as well as magazines holding more than 10 rounds of ammunition.
The bill, which Feinstein, a California Democrat, introduced in the Senate on Thursday afternoon, would exempt firearms used for hunting and would grandfather in certain guns and magazines. The goal of the bill, she said, would be ‘‘to dry up the supply of these weapons over time.’’
Surrounded by victims of gun violence, colleagues in the Senate and House, and several law enforcement officials, and standing near a peg board with 10 large guns attached, Feinstein acknowledged the difficulty in pursuing such legislation, even when harnessing the shock and grief over the shooting of 20 schoolchildren in Newtown, Conn., last month.
“This is really an uphill road,’’ Feinstein said.
Since the expiration of a ban on assault weapons in 2004, there has been a deep reluctance among lawmakers to revisit the issue. They cite a lack of evidence that the ban was effective and a fear of the powerful gun lobby, which has made significant inroads at both the state and federal level in increasing gun rights over the last decade.
Senator Harry Reid of Nevada, the majority leader, recently said during an interview in his home state that he was skeptical about the bill. Feinstein immediately called him to express her displeasure with his remarks.
Many lawmakers, including some Democrats, prefer more modest measures to curb gun violence, like a bill that would enhance background checks of gun buyers or focus on enforcement of existing laws.
One such measure has been introduced by Senator Patrick Leahy of Vermont, a Democrat and chairman of the Judiciary Committee, who will begin hearings next week on gun violence. His bill would give law enforcement more tools to investigate so-called straw purchasing of guns, in which an individual buys a firearm for someone who is prohibited from obtaining one. Among the witnesses will be Wayne LaPierre, the chief executive of the National Rifle Association.
More legislation is expected to arise over the next week or two. Senators Kirsten Gillibrand, a Democrat of New York, and Mark Kirk, a Republican from Illinois, have agreed to work together on gun trafficking legislation that would seek to crack down on illegal guns. Currently, there is no federal law that defines gun trafficking as a crime.
Feinstein was joined Thursday by several other lawmakers, including Representative Carolyn McCarthy of New York, a Democrat who will introduce companion legislation in the House, and Democratic Senator Richard Blumenthal of Connecticut, who emotionally recalled the day when the children and adults were gunned down in Newtown.
“I will never forget the sight and the sounds of parents that day,’’ he said. Several gunshot victims, families of those killed, and others gave brief statements of support for the bill.
Feinstein’s bill — which, unlike the 1994 assault weapons ban, of which she was a chief sponsor, would not expire — would also ban certain characteristics of guns that make them more lethal and would require that grandfathered weapons be registered. More than 900 guns would be exempt for hunting and sporting.
Such a measure is vehemently opposed by the National Rifle Association and many Republican lawmakers, as well as some Democrats.
‘‘I don’t think you should have restrictions on clips,’’ said Senator Tom Coburn of Oklahoma, a Republican who has said he welcomes a Senate debate on guns. ‘‘The Second Amendment wasn’t written so you can go hunting, it was to create a force to balance a tyrannical force here.’’
Bans on assault weapons and high capacity magazines were among the proposals unveiled by President Obama and Vice President Joe Biden last week.
Biden took the campaign for tougher gun laws to the Internet on Thursday in an online video chat that was part of an effort by the White House to build public support for its guns package.