Time-to-crime on Maryland weapons in 2011 was 12.6 years, higher than the national average of 11.2. That means fewer guns in the state were bought with criminal intent but rather found their way into circulation over time, the agency says.

Guns sold in Maryland are less likely than in other states to have a time-to-crime of less than two years. But guns used in crimes also come from other states and account for many of Baltimore's problems, authorities say.

In 2011, 1,707 guns from other states were recovered in Maryland; by comparison, 681 guns from Maryland were recovered in other states. Pennsylvania was the source of 265 of the guns recovered in Maryland, 418 traced back to Virginia and 146 originated in West Virginia.

Each of those states ranks lower than Maryland on the Brady Campaign to Prevent Gun Violence's "scorecards" of states that have strong gun laws. Maryland ranks seventh, but some say Obama's proposal could help narrow the gap.

The plan would require all gun purchasers to pass background checks; limit felons, domestic abusers and the mentally ill from acquiring guns; and close the "gun show loophole" across the nation. That exception allows buyers in many states to avoid background screenings.

About 40 percent of guns are bought without a background check. A recent Johns Hopkins University study on gun policy reform stated that 80 percent of inmates convicted of crimes using handguns said in a national survey that they had obtained the weapon through a transaction with an individual who was not a licensed dealer and thereby skipped official review.

Maryland requires background checks for handgun purchases, even through private sellers.

But background checks are no panacea. ATF data from 2011 indicates that most guns recovered by law enforcement in the state originated here.

John H. Josselyn, legislative vice president of the Associated Gun Clubs of Baltimore, said it's clear that gun laws aren't working in Baltimore. He served on the governor's task force created last year to study access to regulated firearms by the mentally ill and was on another state task force decades ago that studied gun issues.

"We determined that violence is behavior, not technology," he said. "Laws do not control behavior. They simply define unacceptable behavior."

Criminals can get guns without background checks by stealing them, but that only accounts for 10 percent to 15 percent of the guns used in crimes. A much more common method is through "straw purchasers," who buy guns on behalf of someone else, according to several studies using ATF information. Prospective buyers sometimes go through brokers, a study in Chicago showed.

And then there is the black market. Starting in 2007, Michael Papantonakis, an unlicensed dealer, sold guns that included a Walther P38, a Beretta .380, a 9 mm Sig Sauer, a Smith & Wesson 9 mm, a Glock 17, an SKS 7 mm rifle, a Para-Ordnance .45-caliber gun and a Colt MK5 .357-caliber Magnum revolver with a 6-inch barrel to an ATF informant. The prices ranged from $650 to $1,500.

"We're real used to selling to Bloods and Crips," Papantonakis, who operated an Utz potato chips stall in Baltimore's Lexington Market, told the informant in a recorded conversation. He pleaded guilty and received 15 months in federal prison.

John Roman, senior fellow in the Justice Policy Center at the Urban Institute and director of the District of Columbia Crime Policy Institute, which works with the mayor's office in Washington, said illegally obtained guns come from just a few sources. By tracing guns through registration and other methods, as some proposals seek, law enforcement can shut down these covert arms dealers, he said.

"If we have the ability to track those guns, to get guns out of the hands of people with mental illness, of people known to [commit] violent acts, I think that's a positive," said Batts, who supports a requirement that all gun purchases be registered with Baltimore police.

But not everyone thinks tracking guns would make a huge difference.

"There are many ways that guns get into the hands of criminals, but in most of the violent crime cases we prosecute, the criminal obtained the gun without any paper trail," said Rod J. Rosenstein, the U.S. attorney for Maryland. "If you trace the history of the gun, you won't find a transfer to the end user because only licensed firearms dealers are required to report transactions. The last recorded transaction will have nothing to do with the person who committed the crime."

Sheryl Goldstein, who from 2007 to 2012 led Baltimore's policy and legislative efforts against gun crime, said tracking guns requires a lot of effort.

"You can find straw purchasers, but it's an inordinate amount of work and the penalties are not significant," said Goldstein, who now works with the Police Executive Research Forum, a Washington think tank. "The juice is not worth the squeeze. I think the biggest thing you can do that would make a difference in Baltimore City is mandatory minimum penalties."

Baltimore repeatedly pushed in Annapolis to establish a mandatory minimum penalty of 18 months in jail for those caught carrying illegal loaded handguns. City officials cited data showing that those caught with guns often received suspended sentences from judges.