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:

In Richmond in 2003, Michael Antoine Wilson, 21, used his semiautomatic rifle with its 30-round magazine to shoot his 17-year-old girlfriend to death in front of children and relatives. Then he went to a nearby convenience store, killed two workers and stole a van before turning the gun on himself.

In Roanoke in 2004, Marcus Jerome Nance, 22, used his legally purchased 9mm Glock 17 handgun with a high-capacity magazine to spray 33 bullets into a crowd that had gathered outside a Roanoke gas station after a nightclub closing, killing one and wounding two.

In Newport News last year, Antonio Johnson, 34, began shooting at police during a traffic stop with a 9mm semiautomatic handgun outfitted with a 15-round magazine. "Subject shot police officer and then killed himself with weapon," state records say.

In the Arizona shootings, Loughner allegedly used a Glock 19 that he had legally purchased at a Tucson sporting goods store in November. The gun's capacity allowed Loughner to squeeze off more than 30 shots without reloading, authorities said.

The federal assault weapons ban from late 1994 through late 2004 prohibited the manufacturing of magazines capable of holding more than 10 rounds. But the act permitted the sale of magazines manufactured before the ban.

The federal prohibition was spurred by a mass killing in 1989 in Stockton, Calif., where Patrick Edward Purdy, 24, a mentally unbalanced drug addict, fired 110 shots from an AK-47 into a schoolyard, killing five children and wounding 29 others and a teacher. He used a 75-round rotary clip and a 35-round banana clip, one of four he was carrying.

New legislative interest

Rep. Carolyn McCarthy (N.Y.) and 57 other Democrats proposed legislation last week to ban the sale or transfer of high-capacity magazines, no matter when they were manufactured. McCarthy's husband and five others were killed in 1993 on the Long Island Rail Road by a gunman armed with a semiautomatic pistol and four 15-round magazines. He fired 30 shots before being subdued while changing magazines.

The bill's prospects are considered slim in the Republican-controlled House. In the Senate, the National Rifle Association says it has a solid 50-senator pro-gun block that could delay any legislation.

The NRA has announced its opposition to proposals that limit magazine capacity.

"These magazines are standard equipment for self-defense handguns and other firearms owned by tens of millions of Americans," according to a statement on its politics Web page, and in a letter circulating to members of Congress. "Law-abiding private citizens choose them for many reasons, including the same reason police officers do: to improve their odds in defensive situations."

The firearms industry also opposes the proposal. "The tragedy in Tucson was not about firearms, ammunition or magazine capacity," said Ted Novin, a spokesman for the National Shooting Sports Foundation, a gun industry group. "It was about the actions of a madman. Period."

The analysis by The Post is possible because of a little-known database of guns seized in Virginia. The database, called the Criminal Firearms Clearinghouse, has information on more than 100,000 firearms recovered by more than 200 local police departments since 1993. A federal law in 2003, known as the Tiahrt Amendment after the congressman who sponsored it, banned the release of federal data on guns recovered in crimes.

Last year, The Post mined the database to pierce the secrecy imposed by Congress on federal gun-tracing records. The analysis found that a fraction of licensed dealers in Virginia sell most of guns later seized by police. The vast majority of the guns in the database were confiscated because of illegal-possession charges. But thousands were swept up in the wake of assaults, robberies and shootings.

Two months before the ban expired in September 2004, Marcus Nance bought an extended magazine and a 9mm Glock 17 handgun at a Roanoke gun store. Three nights later, down the street from the store, Nance opened fire on a crowded parking lot after arguing and fighting with people in the crowd.

A police officer called to investigate a disturbance heard shots and saw Nance holding a gun at arm's length and firing "randomly into the mass of people" before shooting several rounds into the air.

A police car's dashboard camera recorded the jackhammer sound of gunfire. In a car parked nearby, police found a Glock gun box and two boxes of ammunition, one of them partially empty.

Police went to the gun shop and confirmed that Nance had bought the handgun ($555), a laser sight ($380) and two extended magazines ($135), paying cash in an entirely legal transaction. Police noted: "The magazines in question were manufactured before 1994 and not considered prohibited."

Nance, who said he had been attacked by members of the crowd and shot in self-defense, was convicted of second-degree murder and is in prison.

The 2004 study

Koper's 108-page 2004 study for the National Institute of Justice found the ban on assault weapons had mixed results.

"Assault weapons were rarely used in gun crimes even before the ban," he said in the report. But he also concluded that the prohibition on high-capacity magazines might have affected public safety, because such magazines allow shooters to inflict more damage.

"Tentatively I was able to show that guns associated with large-capacity magazines tended to be associated with more serious crimes, more serious outcomes," he said.

Some gun rights activists argue that a ban on high-capacity magazines would violate the Second Amendment right to bear arms. One prominent gun rights activist who takes a less absolute position is Robert A. Levy, chairman of the Cato Institute. He is also the lawyer who brought the case that overturned D.C.'s handgun ban.

But Levy said the government would need to prove that such a ban was effective.

"The burden is on the government, not on the individual to show that the regulation isn't unduly intrusive," Levy said.

Colin Goddard, a lobbyist for the Brady Campaign to Prevent Gun Violence and a victim of the 2007 Virginia Tech shootings, said the high-capacity ban could save lives. The Virginia Tech shooter, Seung Hui Cho, used several 15-round magazines to fire 174 shots and kill 32 people in the worst gun-related mass murder by an individual in U.S. history.

"When you double and triple the amount of the clip size, you don't double or triple the number of deer you kill, you double and triple the amount of innocent people who are killed in shootings like this," said Goddard, 25, who was shot four times by Cho.

Bradley A. Buckles, ATF director from 1999 to 2004, said bureau officials advised Congress to focus on high-capacity magazines, which were "completely unregulated" and had almost no sporting purpose.

"The whole thing with magazine capacity came out of ATF," Buckles said. "It wasn't so much guns, but it was firepower. What made them more deadly than a hunting rifle was the fact that you could have a 20-round, 30-round clip, when most hunting rifles wouldn't have more than five rounds."

Buckles said lawmakers should have extended the ban on high-capacity magazines in 2004. Banning them now, he said, just puts everyone back at square one.

"There are so many millions of them out there, it probably wouldn't make any immediate difference over the course of 20 years," Buckles said. "It is not a short-term solution to anything."

Research editor Alice Crites and staff writer Sari Horwitz contributed to this story.