Leon jerked back the slide on the tiny, black, .25 caliber automatic pistol, releasing it with a loud snap.

"That's how you cock it, man," he explained, his thin fingers curled around the pistol's creamy pearl grips. "Then you just start pulling the trigger."

The two baby-faced boys watching him glanced at each other and beamed. They wanted to buy a gun so they came to Leon's dingy Northwest Washington apartment late one afternoon last week and rapped on his door.

Leon hustled the youths into the hallway where, he later said, they told him they had $65 and were looking for a "piece."

A few minutes later, he returned, gave the youths the gun, a couple dozen cartridges in a plastic sandwich bag and delivered a five-second lesson on loading and firing.

On the streets, Leon is known as a gun man. When not peddling pot, dealing hot cars or pimping on the side, he swaps hits of heroin for chrome-plated pistols, lends .44 magnum revolvers to career criminals, arranges gun buys in Virginia and Maryland, and grins when he talks about renting youngsters -- some as young as 12 nd 13 -- rusty Saturday night specials for $10 so they can earn enough cash to buy their own piece.

"I had one little dude leave me his bicycle [as collateral]. He was about this big," Leon chuckles, lifting his hand about four feet from his apartment's broken tile floor. "Now that was one scrappy dude." He erupts into laughter, his puffy eyes filling with tears.

Most of the 10 to 15 small caliber, off-brand handguns, which he says he sells each week at prices ranging from $35 to $75, go to teen-agers. He keeps 25 to 40 of the small handguns in a metal foot-locker that also contains dozens of bags of bullets. Lifting the trunk's lid, Leon boasts, "This is my junk box, man. This is what the kids buy."

Children are a safe, easy sale, he says. "The thing about kids," Leon continues, "is that cops don't use 'em undercover and street-smart kids ain't afraid of cops. They just say they found 'em [guns]."

Leon also sells expensive, namebrand guns. Those customers, who pay top prices for Charter Arms .44 magnums and military issue .45 automatics, are not all professional criminals. Many of his customers are city dwellers who want to own a handgun for protection but can't buy one legally because of the city's tough gun law.

D.C. police say the proliferation of handguns is one of the most terrifying aspects of the city's rising crime rate. More juveniles than ever have handguns, Police Chief Burtell M. Jefferson says. Illegal gun trading is rampant on the streets of the nation's capital, which has one of the toughest gun control laws in the country.

"Yes, it's easy to get 'em [guns]," Jefferson says, adding that undercover gun buys are generally "not feasible" because "criminals can just go across the river and get more guns" in Virginia and Maryland.

Jefferson says the best way to reduce the number of guns in this city is by asking residents to surrender their handguns. As part of a 13-point crime prevention program, Mayor Marion Barry has said he will declare a two-week amnesty period soon during which guns can be turned in, no questions asked. If residents give up their guns, burglars will not be able to steal them and the guns will not end up in criminals' hands, Jefferson explains.

Leon's world is not the Washington of splendid marble monuments, bureaucratic briefings or $50 expense account meals, but of flophouses, drunks, hustlers and marks. He spends his days with other sidewalk shufflers who, just like him, survive by schemes and scams, in part because there are only so many regular jobs for grade school drop-outs and kids with criminal records.

Moments after his two teen-aged customers had gone, Leon joked about selling them the .25 automatic. "Hey, they probably got it to protect some old lady when they help her cross the street," he said.

Seconds later, he exploded, irritated by the question. "Why the hell do you think they bought it, man? I ain't no babysitter. The streets are mean, man. If I weren't selling it, someone else would.

"You learn fast in the streets or you don't make it," he snapped. "I help kids grow up fast."

For the past five years, it has been illegal for District residents, except for law enforcement officers and their gun suppliers to buy or sell handguns in the city. The only private citizens in Washington who can legally own a handgun are gun owners who registered their handgun during a special 60-day period in 1976. Since then, it has been impossible for a Washington resident to legally buy a handgun or bring one into the city.

That strict gun law, however, has not dried up the city's streets arsenal. Since it took effect, D.C. police have been taking an average of eight guns each day off Washington's streets or about 3,000 handguns a year. Most eventually are shipped to Baltimore where they are melted and made into manhole covers.

As soon as one gun is confiscated, police say, another hits the streets.

"We get them in here by the cart full," one First District detective says in disgust. "Hell, sometimes it seems like an armed camp out there. You wonder -- is everyone on the streets carrying a piece?"

"How many guns are in Washington?" says George Wilson, head of the D.C. firearms investigation unit, responding to a reporter's question. "There is no way to even guess. But there are an awful lot out there."

Wilson has been building a reference library of guns for the police department since 1970. So far, he has more than 1,500 different firearms that were used in District crimes. The guns include Communist-manufactured machine guns, World War II pistols from Japan, and hundreds of sophisticated, hand-crafted revolvers displayed next to bargain basement pistols.

"It's like a grocery store out there, man," Leon says. "You can get anything you want if you got the cash."

Selling handguns illegally in Washington is a lucrative business, Leon says. "Everybody wants one." While a stolen television can be resold for only a fraction of its original value, a stolen handgun will cost nearly as much as a new one -- sometimes even more, if the buyer wants a gun that cannot be traced.

Similar to the way it was with liquor in prohibition days, Washington has developed an underground of gun speakeasies. In only four days, a reporter unfamiliar with Washington's street world was able to locate self-styled gun dealers who claimed they could deliver a .45 caliber submachine gun for $400 within a week or put together deals involving 50 to 100 guns.

The best indicator of how easy it has become to get handguns here, however, does not come from police statistics or reporter's queries, but from the gun buyers themselves.

Last September, a 16-year-old student at Springarn High School in Northeast was shot and killed while several students were examing a .25 caliber automatic. A week later, at another school, a teacher took a .25 caliber automatic from a 16-year-old student who had dropped it.

After the Spingarn shooting, a student, called Chico explained: It's a fame thing. You carry a gun in your bag and you cool, man. You walk down the hall and you know that if anybody bump you, you got a gun to do your talking.

"Guns is real big with the craps players," he continued. "It's that whole underworld trip that people are into. Talking tough, acting tough, being a dude."

Leon says he gets most of his stolen guns from junkies. "A junkie, he'll swap for a fix." He also can buy from "gun runners" who make regular trips to states where it is easy to buy guns. In 1976, federal Alcohol, Tobacco and Firearms (ATF) agents identified five states, including Virginia, as being major gun supply points for the entire country.

Finally, Leon has his own network. If someone wants a specific handgun and is willing to pay top price, Leon will contact "relatives" in Virginia or Maryland who will buy the gun from a legal gun dealer. Leon splits his $50 finder's fee with his "relatives" who later report the gun lost or stolen.

Realizing Washington's gun problem was worsening, the ATF reorganized its field office here four months ago, with the top priority being to get illegal handguns off Washington streets.

Special agent Ed Easley from Oklahoma City was put in charge of the Washington office, which includes the District, Maryland and Delaware, and parts of Virginia and West Virginia. Michael J. Bregman, a New York City agent, was named Easley's assistant.

"We've been told that Washington is virgin territory," says Bregman, "and we're going to do something about it."

Easley's first request was to move the ATF district office from Falls Church to Washington where "the guns are."

ATF agents and D.C. police also have launced Project Lead, a trace program which will help police learn how recently purchased guns get into the city. It also will pinpoint major gun dealing areas. A similar program in New York led to the arrest of several major gun dealers, Bregman said.

In July, a confidential ATF strategic intelligence report concluded that nearly 40 percent of handguns used in Washington crimes came from Virginia or Maryland gun dealers. For example, the .38 caliber gun allegedly used to kill cardiologist Michael Halberstam at his Northwest Washington home late last year was stolen during a Virginia burglary.

To stop gun runners from buying in states near Washington, ATF has developed a profile of gun runners and their techniques, Easley says, similar to profiles used by airports to identify hijackers.

Easley also reassigned his agents, boosting the Washington squad from 10 to 35 agents, more than half of his 60-agent force. He also has asked for three more agents.

"We are very serious about this," Easley says.

Leon is serious, too. "There are ain't-gots and have-gots in this world," Leon philosophizes while lighting another cigarette. "And that means we're gonna have guns. The have-gots want 'em to protect what they got. The ain't-gots want 'em to get what they ain't got."

Leon picks up one of his cheap pistols. "Me, why I'm just providing a community service, man."