The number of guns with high-capacity magazines seized by Virginia police dropped during a decade-long federal prohibition on assault weapons, but the rate has rebounded sharply since the ban was lifted in late 2004, according to a Washington Post analysis.

More than 15,000 guns equipped with high-capacity magazines - defined under the lapsed federal law as holding 11 or more bullets - have been seized by Virginia police in a wide range of investigations since 1993, the data show.

The role of high-capacity magazines in gun crime was thrust into the national spotlight two weeks ago when 22-year-old Jared Lee Loughner allegedly opened fire with a semiautomatic handgun outside a Tucson grocery store, killing six and wounding 13, including Rep. Gabrielle Giffords (D-Ariz.). Authorities say Loughner used a legally purchased 9mm Glock 19 handgun with a 31-round clip and was tackled while changing magazines.

Of the seized Virginia weapons, 2,000 had magazines with a capacity of 30 or more bullets. Some states still limit magazine capacity. California, for example, limits them to 10 and Maryland to 20.

Last year in Virginia, guns with high-capacity magazines amounted to 22 percent of the weapons recovered and reported by police. In 2004, when the ban expired, the rate had reached a low of 10 percent. In each year since then, the rate has gone up.

"Maybe the federal ban was finally starting to make a dent in the market by the time it ended," said Christopher Koper, head of research at the Police Executive Research Forum, who studied the assault weapons ban for the National Institute of Justice, the research arm of the Justice Department.

Congress is considering legislation to reinstitute the assault weapon ban's prohibition on high-capacity magazines, a measure strongly opposed by gun rights advocates.

The analysis of the Virginia records, obtained under the state's public information law, provides a rare window into the firepower of guns used in crimes. The Bureau of Alcohol, Tobacco, Firearms and Explosives, which traces guns for local police agencies and regulates the firearms industry, does not track magazine sizes. Academic researchers said they were unaware of any other comprehensive study of firearms magazines.

The pattern in Virginia "may be a pivotal piece of evidence" that the assault weapons ban eventually had an impact on the proliferation of high-capacity magazines on the streets, said Garen Wintemute, head of the Violence Prevention Research Program at the University of California at Davis.

"Many people, me included, were skeptical about the chances that the magazine ban would make a difference back in 1994," Wintemute said. "But what I am seeing here is that after a few years' lag time the prevalence of high-capacity magazines was declining. The increase since the ban's repeal is quite striking."

Guns with high-capacity magazines have appeared in Virginia crimes ranging from the mundane to the murderous. The Post found that 200 guns with high-capacity magazines figured in Virginia homicides, including these incidents: