Sonia Mangum of Stevensville expressed concern that if attacked, she might need more than 10 rounds in a magazine — O'Malley's proposed limit — to protect herself.
"If I'm under duress, I'm going to be missing and may not have time to reload," she said.
Stephen Schneider of the Maryland Licensed Firearms Dealers Association, based in Towson, said gun licensing and the weapons ban would cause gun shops to lay off employees and close. He said the state has some of the strictest gun controls in the nation and that more restrictions "will not make us safer."
Senators also heard from Jeff Reh, a director of Beretta U.S.A. Corp. of Accokeek, a firearms manufacturer and distributor that is a major employer in Senate President Thomas V. Mike Miller's home turf in southern Prince George's County.
Reh testified that Beretta was committed to Maryland but issued a veiled threat to leave if the bans on assault-type weapons and high-capacity magazines are adopted.
"We are confronted with a state government that wants to ban our products at a time, by the way, when numerous other state governments are courting our investment."
Maryland Attorney General Douglas F. Gansler joined a parade of law enforcement officials speaking in favor of the governor's bill, arguing for what he called "reasonable" regulations of gun ownership.
"Most people believe today you shouldn't be able to own grenades or drive a tank down Pratt Street," he said. "I see no reason why anyone should have assault weapons."
Gansler also endorsed the other provisions of O'Malley's bill, including the proposed licensing requirement for owning handguns.
"We ask folks to get a license to drive a car and get some training before they do," he said. Later in the hearing, a representative of the National Rifle Association countered that driving a vehicle was not mentioned as a right in the U.S. Constitution.
Baltimore County Executive Kevin Kamenetz spoke in favor of the ban on assault-type weapons, recalling two gun incidents in county schools last fall, one in which one student shot another student with a shotgun.
"This is not a cure-all here," he said. "If the 15-year-old at Perry Hall [high school] had come in with an assault weapon, we would have been Newtown."
Baltimore's police commissioner, Anthony W. Batts, also spoke emphatically in favor of licensing. He recalled growing up in a tough part of Los Angeles where he saw guns "taking lives." While he was supportive of a right to own a gun for self-defense, he asked, "Are we willing to do anything to keep young people safe in our communities?"
Some legislative leaders have suggested that the governor's bill should be broken into separate pieces. But Stacy Mayer, O'Malley's chief legislative officer, said the administration prefers to keep the package as one.
In the House of Delegates, Speaker Michael E. Busch has sent it to two committees, increasing the chances that the bill will get to the floor. Busch also formed a work group of 15 lawmakers who have been getting private briefings from gun-control advocates, gun manufacturers and public safety experts.
Another part of O'Malley's plan aims to keep guns away from people with mental illnesses by more often requiring reporting to the state when patients are treated. The information would be sent to the state and federal databases consulted during background checks and would disqualify about 2,000 people each year from gun ownership in Maryland, according to the Department of Mental Health and Hygiene.
It would also put into a federal database the names of about 50,000 people who are now prohibited from buying guns in Maryland but who currently could clear a background check in another state.
Baltimore Sun reporter Erin Cox contributed to this article.