Rep. Carolyn McCarthy (D-N.Y.) will introduce legislation next week capping ammunition magazines at 10 bullets, she announced Thursday.

McCarthy, whose husband was killed during a commuter train shooting in 1993, has said all week that she'd be proposing legislation to ban high-capacity clips like those allegedly used in Saturday's shooting in Arizona. But she hadn't specified the maximum number of bullets, hoping instead that some flexibility on her part might entice GOP leaders to support the bill.

Since the tragedy, however, Republican leaders have aligned themselves squarely against gun reforms proposed even by members of their own party.

The 1994 assault-weapons ban included the same 10-bullet cap, but that law expired in 2004.

Like the assault-weapons ban, McCarthy's bill will ban high-capacity magazines manufactured after the law is enacted — meaning it doesn't prohibit possession of those made beforehand.

The New York Democrat said it's impossible to estimate the effects of her proposal, but it will "ultimately save lives."

"The only purpose for the existence of these devices is to be able to shoot as many people as possible as quickly as possible," McCarthy wrote Thursday in a "Dear Colleague" letter to House members. "There is no reason that these devices should be available to the general public."

McCarthy is scheduled to introduce the bill formally on Tuesday.