Wash. Where guns used in crimes came from Me. Arrow sizes show the number of guns traced to other states in 2014 Mont. N.D. Minn. Vt. Ore. N.H. Idaho N.Y. Wis. S.D. Mass. Mich. R.I. Wyo. Conn. Pa. Iowa N.J. Neb. Nev. More than two-thirds of guns connected to crimes in New York and New Jersey were brought in from other states, mostly from the South. Md. Ohio Del. Utah Ill. W.Va. Colo. D.C. Ind. Va. Kan. Mo. Calif. Ky. N.C. Tenn. Okla. 1,184 guns from arizona N.M. Ark. S.C. Ariz. Ga. Ala. Miss. Criminals in California used about 6,000 guns from other states, mainly from those with few gun-buying restrictions like Arizona and Nevada. La. Texas Crime rings smuggle guns from Orlando, Fla., to Puerto Rico. Fla. 349 guns from florida State gun control laws LENIENT strict Puerto Rico Where guns used in crimes came from Arrow sizes show the number of guns traced to other states in 2014 Ore. N.Y. N.J. Nev. Illinois Indiana Calif. N.C. Ariz. S.C. 1,184 guns from arizona Ga. Texas Florida State gun control laws 349 guns from florida LENIENT strict Puerto Rico Where guns used in crimes came from Wash. Arrow sizes show the number of guns traced to other states in 2014 Me. Mont. N.D. Minn. Vt. Ore. N.H. Idaho N.Y. Wis. S.D. Mass. Mich. Wyo. Pa. Iowa N.J. Neb. Nev. Md. Ohio Utah Most guns connected to crimes in New York and New Jersey were brought in from other states, mostly from the South. Ill. W.Va. Colo. D.C. Ind. Va. Kan. Mo. Calif. Ky. N.C. Tenn. 1,184 guns from arizona Okla. N.M. Ark. S.C. Ariz. Ga. Ala. Miss. La. Texas Criminals in California used about 6,000 guns from other states, mainly from those with few gun-buying restrictions like Arizona and Nevada. 349 guns froM florida Fla. State gun control laws Crime rings smuggle guns from Orlando, Fla., to Puerto Rico. Puerto Rico LENIENT strict Where guns used in crimes came from Washington Arrow sizes show the number of guns traced to other states in 2014 Me. Montana North Dakota Minnesota Vt. Oregon N.H. Idaho New York Wisconsin South Dakota Mass. Michigan R.I. Wyoming Conn. Pa. Iowa New Jersey Neb. Nevada Md. Ohio More than two-thirds of guns connected to crimes in New York and New Jersey were brought in from other states, mostly from the South. Del. Utah Illinois W.Va. Colorado D.C. Indiana Va. Kansas Mo. California Ky. N.C. Tenn. Oklahoma 1,184 guns from arizona New Mexico Arkansas S.C. Arizona Georgia Alabama Miss. Criminals in California used about 6,000 guns from other states, mainly from those with few gun-buying restrictions like Arizona and Nevada. Texas Crime rings smuggle guns from Orlando, Fla., to Puerto Rico. Louisiana Florida State gun control laws 349 guns from florida LENIENT strict Puerto Rico

In California, some gun smugglers use FedEx. In Chicago, smugglers drive just across the state line into Indiana, buy a gun and drive back. In Orlando, Fla., smugglers have been known to fill a $500 car with guns and send it on a ship to crime rings in Puerto Rico.

In response to mass shootings in the last few years, more than 20 states, including some of the nation’s biggest, have passed new laws restricting how people can buy and carry guns. Yet the effect of those laws has been significantly diluted by a thriving underground market for firearms brought from states with few restrictions.

About 50,000 guns are found to be diverted to criminals across state lines every year, federal data shows, and many more are likely to cross state lines undetected.

In New York and New Jersey, which have some of the strictest laws in the country, more than two-thirds of guns tied to criminal activity were traced to out-of-state purchases in 2014. Many were brought in via the so-called Iron Pipeline, made up of Interstate 95 and its tributary highways, from Southern states with weaker gun laws, like Virginia, Georgia and Florida.

New York The Iron Pipeline Pa. Guns used in recent shootings of New York City police officers were traced to pawn shops in Georgia. JONESBORO Va. New Jersey 386 guns N.C. PERRY Ga. S.C. Many guns used in crimes are brought to New York and New Jersey along Interstate 95. In recent years, more guns have started coming from Pennsylvania gun shows, a federal official said. 292 guns Fla. New York Pa. New Jersey Guns used in recent shootings of New York City police officers were traced to pawn shops in Georgia. Va. N.C. S.C. JONESBORO 386 guns The Iron Pipeline PERRY Many guns used in crimes are brought to New York and New Jersey along Interstate 95. In recent years, more guns have started coming from Pennsylvania gun shows, a federal official said. Ga. 292 guns Fla.

A handgun used in the killing of two Brooklyn officers last year was traced to a pawnshop just south of Atlanta. A revolver used in a fatal shooting of an officer in Queens in May was traced to a roadside pawnshop, also in Georgia, about 100 miles from Atlanta. And a handgun used to kill an officer in East Harlem last month was traced to South Carolina.

“We’re trying to deal with it, but we have a spigot that’s wide open down there and we don’t have a national or local ability to shut that spigot down at the moment,” said the New York City police commissioner, William J. Bratton, as he announced an indictment against gun traffickers last week.

New York Police Department, via Getty Images New York Police Department Two guns used in killings of New York City police officers were traced to pawnshops in Georgia.

The economics are straightforward: A low-quality handgun that sells for $100 in an Atlanta store might sell for $500 or $600 in New York City, researchers say — and it can be transported cheaply. By contrast, the majority of guns used in crimes in Texas, Georgia and other states with more lenient gun laws are purchased in-state.

The New York Times examined gun trafficking by analyzing nine years of data compiled by the Bureau of Alcohol, Tobacco, Firearms and Explosives, as well as an index of state gun laws developed by researchers at Johns Hopkins University.

Law enforcement officials express frequent frustration that they are not able to track every gun that crosses state lines, which means the estimates here are conservative. When the police do recover a gun tied to criminal activity, typically after an arrest, they can trace the gun to where it was last sold through a federally licensed dealer.

Chicago offers perhaps the starkest example of trafficking. There are no retail gun dealers within city limits, because Chicago has some of the tightest municipal gun regulations. Yet bringing a gun into Chicago can be as simple as driving less than an hour to a gun show in Indiana, where private sales are not recorded and do not require a background check.

“If you’re in the city of Chicago on the South Side, you may be closer to Indiana than you are to the Magnificent Mile,” said Roseanna Ander, executive director of the University of Chicago Crime Lab, referring to a well-known part of Chicago’s downtown.

The Route Into Chicago Wisconsin Most guns used in crimes in Illinois were recovered in the Chicago area. Michigan Iowa CHICAGO 1,041 guns Illinois Gun shows in Indiana are a frequent source for guns used in crimes in Illinois. Indiana Missouri Many people in Illinois have family ties to Mississippi, the second most common source for crime guns. The Route Into Chicago Most guns used in crimes in Illinois were recovered in the Chicago area. Wisconsin Iowa CHICAGO 1,041 guns Illinois Indiana Gun shows in Indiana are a frequent source for guns used in crimes in Illinois. Many people in Illinois have family ties to Mississippi, the second most common source for crime guns. Missouri

Many guns follow a complex path from the original sale to the underground market. Most guns are originally bought from retail stores, but people who can’t pass a background check typically obtain guns from friends, family or illegal dealers.

According to an anonymous survey of inmates in Cook County, Ill., covering 135 guns they had access to, only two had been purchased directly from a gun store. Many inmates reported obtaining guns from friends who had bought them legally and then reported them stolen, or from locals who had brought the guns from out of state.

One inmate said, “Some people get on a train and bring them back, can be up to five or six guns, depending on how much risk they want to take.”

Some larger traffickers use more elaborate techniques. Buying a gun in Puerto Rico requires an expensive permit and a lengthy application process, but Florida has no such restrictions. Traffickers in Orlando tied to organized gangs in Puerto Rico send guns in the mail, through FedEx, or even encased in cars that travel by ship to the island.

“They’ll buy a $500 car and stuff it with as many guns as possible,” said Carlos Gonzalez, an agent with the Miami division of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Guns by Mail Orlando, which has a large Puerto Rican population, is the source for many guns trafficked to Puerto Rico. ORLANDO Florida MIAMI 349 guns In 2014, more guns used in crimes in Puerto Rico were traced to purchases in Florida than on the island itself. Cuba Puerto Rico Haiti Dom. Rep. Guns by Mail Orlando, which has a large Puerto Rican population, is the source for many guns trafficked to Puerto Rico. ORLANDO Florida MIAMI 349 guns Cuba Haiti Dom. Rep. In 2014, more guns used in crimes in Puerto Rico were traced to purchases in Florida than on the island itself. Puerto Rico

Federal agents and postal inspectors have caught some traffickers, leading to modified techniques, such as shipping guns in newer, more expensive cars or mailing guns from Jacksonville, Fla., instead of Orlando. Stopping such smuggling is logistically hard. “If the U.S. Postal Service were to screen every single package that entered into Puerto Rico, it would bring the economy to a halt,” Mr. Gonzalez said.

Most gun trafficking patterns have remained remarkably constant over time. But some researchers point to a significant shift in Missouri as evidence that changes to one state’s laws can have broad implications.

Before 2007, Missouri required gun buyers to get a state permit and to undergo background checks on private sales, two restrictions strongly associated with states that provide fewer guns to interstate traffickers, according to research by Daniel Webster, director of the Johns Hopkins Center for Gun Policy and Research. At the time, nearly half of the guns used in crimes and recovered in Missouri were traced to other states, largely from neighboring Kansas and Illinois.

But when Missouri relaxed its gun control laws in 2007, the flow started to change. The number of guns traced to other states decreased, while the number of guns from within Missouri increased to nearly three-quarters.