Dianne Feinstein
U.S. Sen. Diane Feinstein (D-Calif.) introduced an assault weapons ban bill in Congress that will not be a part of the Democrat's base plan for gun control. It will instead become an amendment. Reuters

U.S. Sen. Dianne Feinstein, D-Calif., will introduce a new bill banning assault weapons and high-capacity ammunition clips on Thursday, according to multiple reports.

The legislation will expand the criteria used for classifying military-style assault weapons to ban more than 100 types of weapons, including certain semiautomatic rifles, handguns and shotguns that can hold more than 10 rounds of ammunition.

Firearms used for hunting would be exempt. In addition, the measure would grandfather in guns and magazines owned before the law’s enactment. Those weapons would be recorded in a national registry.

Feinstein, a longtime advocate of gun safety laws, said she is ready to for the tough and potentially combustive fight ahead of her. The National Rifle Association in particular, the nation’s most influential gun lobby, has vowed to protest any measures intended to tighten firearm regulations, which the group says violates Americans’ constitutional right to own firearms.

“I have worked on this for a long time,” Feinstein told USA Today, explaining she is aware of the opposition the new bill will face. “I’m not a newcomer or novice to guns.”

Calls to renew an assault weapons ban, which expired in 2004, became rampant following the December 2012 mass shooting at a Connecticut elementary school. Twenty small children were killed during the rampage, leading President Barack Obama to call for comprehensive gun safety measures for the first time in his presidency.

But the measure is likely to face opposition from many sides -- even from Feinstein’s own party. Senate Majority Leader Harry Reid, D-Nev., has said he opposes banning assault weapons, which is unlikely to pass in the Republican-controlled House of Representatives. Instead, Reid has said he is open to moving on individual aspects on Obama’s gun safety package.