Ahead of the vote, Sen. Chuck Grassley (R-Iowa) said Feinstein's amendment violated Second Amendment rights.
Democrats have been pushing for stricter gun laws since December, when a gunman killed 20 first-graders and six school employees at Sandy Hook Elementary School in Newtown, Conn.
Feinstein said the Sandy Hook massacre “shocked the conscience of America.”
“Over the years as I’ve watched, I’ve come to see that these weapons are attractive to certain types of people: gun collectors, target shooters, hunters, but death tolls show that there is another group that covets these guns even more … their goal is to kill indiscriminately. … The question is, can this group of people who will kill with these weapons, buy these weapons easily, the answer is yes.”
Feinstein said her amendment had one purpose “to dry up the supply of assault weapons and high capacity firearms.” Her amendment would have banned the future manufacturing, imports and sales of certain assault weapons, but would not have taken the guns away from those who already legally own them.
The Senate was scheduled to vote on nine amendments Wednesday, all of which were subject to a 60-vote threshold. More amendment agreements are possible later this week.