"We've tried to take my bill from '94 to 2004 and perfect it," the California Democrat said on the NBC "Meet The Press" program.
Feinstein authored a federal ban on assault weapons in 1994, a ban that was allowed to expire by Congress during the George W. Bush administration. On NBC today, Feinstein agreed with gun control proponent Michael Bloomberg, the New York mayor, who said he wants "weapons of war off the streets of our cities."
On the NBC program, California's senior senator said her lawyers have carefully crafted a constitutional bill that will "exempt over 900 specific weapons that will not ... fall under the bill."
She said the 1994 assault rifle bill that she wrote was never challenged in court by the National Rifle Association.
"Back in '93, when I told Joe Biden who was chairman of the Judiciary Committee that I was going to move this as an amendment on the Crime Bill, he laughed at me," Feinstein said.
"He said, `you're new here. Wait till you learn'," Feinstein related. "And we got it through the Senate, we got it through the House, the White House came alive and ... the bill was passed.
The NRA has declined to comment on gun issues since Friday's slaying of 20 grade school children and seven adults in Connecticut.
Police have said the children were shot multiple times in rapid succession, but have not said if the murder weapons had been in automatic mode -- -- illegal under current laws, or semi-automatic mode -- possibly illegal under the 1994 law.
Feinstein, who just won her fourth Senate election, was propelled to the forefront of California politics when she suddenly became mayor of San Francisco when two politicians were murdered there in 1978. She has been a leading voice for gun control since then.
Feinstein's quotes were transcribed by NBC News.