By Sharon Bernstein
SACRAMENTO, Calif. April 24 (Reuters) - A bill banning the sale of single-shot handguns that can be modified into semi-automatic weapons advanced in the California legislature on Thursday as lawmakers sought to close what the bill's supporters say is a loophole in the state's gun safety laws.
Gun control advocates say thousands of weapons are sold in California each year without a required safety feature that indicates when a bullet is in the chamber, endangering children and others who may be shot accidentally.
"Right now there is a very large opening in the law that permits guns that otherwise we wouldn't consider safe for sale and purchase in California," said Sacramento assemblyman Roger Dickinson, a Democrat who authored the bill.
Under existing law, semi-automatic weapons must have an indicator showing when there is a bullet in the chamber. But many manufacturers do not include the feature, leading some dealers to convert guns to single-shot weapons before selling them, just to change them back later, Dickinson said.
The most populous U.S. state has some of the nation's strictest gun control laws, and Dickinson's measure is the latest of dozens of bills introduced in the state in the wake of mass shootings in 2012 in Colorado and Connecticut.
Last fall, Democratic Governor Jerry Brown, who has tacked to the center despite large Democratic majorities in the legislature, vetoed several of the bills, rebuffing efforts by fellow Democrats to enact a sweeping expansion of firearms regulation.
The proposed ban on converted semi-automatics without the safety feature is a priority for the Brady Campaign to End Gun Violence, said the group's legislative expert, Amanda Wilcox.
The loophole was created after single-shot weapons were exempted from the safety requirement to protect collectors of antique guns, Dickinson said.
After the rule went into effect in 2007, the number of guns being sold as single-shot weapons in the state skyrocketed, which Dickinson said indicated many were being converted.
In 2013, more than 18,000 single-shot gun sales were registered in the state, up from 134 in 2007, the state says. But Assemblyman Brian Jones, a San Diego-area Republican who voted against the bill, said that doesn't mean all purchasers are trying to get around the law.
The National Rifle Association said the measure would hurt law-abiding citizens by "eliminating the only options for Californians to purchase numerous handguns that are commonly owned throughout the rest of the country."
The bill passed the assembly 48-25, and goes to the state senate. (Reporting by Sharon Bernstein; Editing by Cynthia Johnston and Cynthia Osterman)