WASHINGTON — Sen. Dianne Feinstein on Thursday announced legislation 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, D-Calif., said she would introduce Thursday afternoon in the Senate, 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 pegboard with 10 large guns attached, Feinstein acknowledged the difficulty in pursuing such legislation, even when harnessing the shock and grief over the shooting last month of 20 children and six adults at SandyHook Elementary School in Newtown, Conn.

“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 both 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 past decade.

Sen. 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 gunviolence, such as a bill that would enhance background checks of gun buyers or focus on enforcement of existing laws.

One such measure has been introduced by Sen. Patrick Leahy, D-Vt., chairman of the Senate Judiciary Committee, who will begin hearings next week on gun violence. His bill would give law enforcement officials 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 on his own.

While Leahy has said he supports a limit on magazines, he has expressed skepticism about a broad assault-weapons ban. Many gun-control groups have set more modest goals, focusing on gun trafficking and the tracking of mentalhealth records.

More legislation is expected to arise over the next week or two. Sens. Kirsten Gillibrand, D-N.Y., and Mark Kirk, R-Ill., 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 Rep. Carolyn McCarthy, D-N.Y., who will introduce companion legislation in the House, and Sen. Richard Blumenthal, D-Conn., 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 thatday,” he said. Several gunshot victims, family members 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 after being enacted - also would ban certain characteristics of guns that make them more lethal and would require that grandfathered weapons be registered. More than 900 kinds of 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 Sen. Tom Coburn, R-Okla., 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.”

President Barack Obama has called on Congress to act on some gun restrictions.

Vice President Joe Biden said Thursday that he’s more concerned about limiting the number of rounds in a gun magazine than about banning assault weapons that account for a small percentage of gun deaths.

Biden argued that the gunman in Newtown could have been slowed down if he had fewer rounds in each magazine and had to change clips more often. “Maybe if it took longer, maybe one more kid would be alive,” Biden said during an online video chat on Google Plus.

Information for this article was contributed by Jennifer Steinhauer of The New York Times and by Erica Werner, Nedra Pickler and Susan Haigh of The Associated Press.

Front Section, Pages 2 on 01/25/2013