APRIL 11, 1986, was the bloodiest day in FBI history. The bank robbers were ex-soldiers turned psychopaths, a pair of expert marksmen armed with semiautomatic weapons — and they had no intention of surrendering. After a four-minute firefight on the streets of Miami, both gunmen were killed by a heroic agent. The toll for the FBI was terrible: Two agents dead, three permanently crippled, and two more severely injured. "Gun Battle Looked Like the O.K. Corral," The Palm Beach Post declared.

Lt. John H. Rutherford of the Jacksonville, Fla., Sheriff's Office heard about the shoot-out later that day. "The bad guys," he recalled, "were starting to carry high-capacity weapons." In the chaos of the shoot-out, the federal agents struggled to reload their revolvers, jamming cartridges one after another into five- and six-shot Smith & Wessons. One bank robber, armed with a Ruger semiautomatic rifle, merely had to snap a new magazine into his gun to have another 20 rounds instantly. His partner carried a 12-gauge shotgun with extended eight-round capacity. They were armed for a small war. The FBI had revolvers.

"That was a scary, terrible thing to hear about," said Rutherford. "If the FBI is outgunned, something is wrong." This perception was widely shared by cops, politicians, and law-abiding firearms owners: The criminals were now better armed than the forces of order. The next year Rutherford received the assignment to recommend a new handgun to replace the Smith & Wesson revolvers that his department issued. His counterparts in hundreds of local, state, and federal police agencies were given similar missions.

"My job," Rutherford told me, "was to find a better gun."

RUTHERFORD HAD HUNTED as a boy and liked guns. He kept a framed copy of the Second Amendment on his office wall and taught his two children to shoot. He carried a handgun at all times, on and off duty — even to church on Sunday, which annoyed his wife. But as of 1987, he had little experience with semiautomatic pistols. He knew only revolvers. So he had the department hire an outside consultant to help sort through the many options on the market. He chose Emanuel Kapelsohn, a well-known firearms trainer.

Gun manufacturers from all over the world sent the sheriff's office their latest models, a dozen in all. Rutherford and a brain trust of fellow officers with firearms expertise gathered to examine the candidate guns. "I pull out this black box and pop the thing open, and here's this Glock," Rutherford recalled. "I'm like, 'What the heck is this?' I'm tapping it on the table. It's plastic! What the hell? And there's no hammer on this thing. I literally said, 'We don't want any crap like this,' and I slung it over onto the couch."

Kapelsohn noticed the discarded Glock. "You need to give it a chance," he said.

His words carried weight. Kapelsohn, who came from New Jersey, had a national reputation and heavy connections at the National Rifle Association. His credentials were unusual in the weapons-training business: He held a B.A. in English literature from Yale and a law degree from Harvard.

Kapelsohn's suggestion that the Austrian pistol be taken seriously proved prescient. Within a few days, "we were fighting over who was going to get the Glock," Rutherford said. "It's just like shooting a revolver, and that's what everybody liked about it. You pull it out, you pull the trigger, and you put it away. That was the beauty of it."

The Glock had another advantage: a light, steady trigger pull. The Smith & Wesson .38-caliber guns in use in Jacksonville had a heavy pull of 12 to 14 pounds — standard for revolvers. Shooters who train regularly can achieve accuracy with a heavy trigger. But only a small minority of cops practice diligently. The average officer is a mediocre shot, or worse.

With a Glock, poor marksmen become adequate; moderately skilled shooters begin grouping rounds in small bunches near dead center of their target. The pistol's gentle five-pound trigger action doesn't require the sort of muscular squeeze that can cause the user to jerk the gun off target.

When word got out that Rutherford was leaning toward the Glock, some of his superiors warned him that could be risky. "Now, John," he recalled one senior officer telling him, "you know the sheriff and the undersheriff, they really like Smith & Wesson." Smith & Wesson was what the Jacksonville Sheriff's Office had always known. It was the American cop's brand.

But Rutherford was adamant. He had worked for months on his report, he said. "Now you want me to change it to something else that I know is not the best gun?" During a two-hour presentation to the sheriff, he stressed the Glock's accuracy and safety advantages, as he saw them. He explained that the Austrian pistol was much easier to maintain because it had only 34 parts; the Smith & Wesson 645 had more than 100. And as beloved as the brand had been, Smith & Wesson had allowed its manufacturing quality to slip, Rutherford told his superiors. Out of a shipment of 40 new Smith & Wesson revolvers, three or four would malfunction right out of the box.

A decision came quickly: "We're buying Glocks," the sheriff said.

An order went to Glock for 900 pistols to arm the Jacksonville force. Over the next six months, more than 100 police agencies around the country requested copies of Rutherford's 90-page report on Glock.

Twenty-two years later, the Jacksonville Sheriff's Office, which Rutherford now presides over as sheriff, has 1,700 officers. It still arms them with Glock pistols.

EMANUEL KAPELSOHN'S RECOMMENDATION of the Glock wasn't happenstance. In mid-1986, Karl Walter, an energetic Austrian gun salesman, began putting some of the country's most admired shooting instructors on contract to spread the word about Glocks. This melding of training and marketing became a company hallmark, and Kapelsohn was one of the specialists Walter hired.

In some cities, the Glock gun instructors were paid by the local authorities; that's the way it worked in Jacksonville. In other situations, Glock dispatched Kapelsohn or another trainer as part of the procurement deal — a freebie for the new customer.

After Jacksonville placed its order for the Glocks, the company sent Kapelsohn back to Florida to provide transitional training on the company's dime. "Karl Walter had the genius at that time to take the training programs on the road," Kapelsohn said. "You had to go to the Smith & Wesson Academy if you were going to use the Smith & Wesson. If your agency was going to adopt the Glock, [Walter] would send some training your way." Many times, instructors from neighboring agencies attended these sessions out of curiosity, or Glock would sponsor an open-house seminar for all federal, state, and municipal trainers in a given region. "The effect of it was to get Glocks in the hands of instructors all over the country," Kapelsohn explained. "This was just a brilliant way to sell this gun."

Until the early '80s, Walter roamed the United States in a motor home customized as a rolling arsenal. Once he was exclusively the lead salesman for the Glock, he still visited trade shows, government agencies, and small towns like Marietta, Ga., making deals. In Marietta, he won over the police chief in 1988 by promising to arm his 100-person force for free. The Marietta PD simply exchanged 126 old handguns for 100 new Glock 17s. The deal worked financially because of the company's startlingly low manufacturing costs, which Glock was able to push down even further — to less than $100 a unit — as its production volume grew. The plastic gun was finding steady acceptance among U.S. law enforcement, but the biggest prize was still out there: New York.

New York City has the largest police force in the United States, with 35,000 officers — more than twice the size of the FBI. Other departments take cues from the NYPD. At the same time, New York itself is not a gun-friendly jurisdiction. It has strict local gun-control laws. And while the state troopers based upstate in Albany were receptive to Glock, the leadership of the NYPD imposed a brand-specific ban on the Austrian gun in early 1986, based on fears that the plastic gun could elude metal detectors.

Despite that, in May 1986 a contingent of New York police trainers invited Walter to make an unofficial presentation at the department's range. To his surprise, 20 firearms instructors showed up; he had brought only a handful of sample pistols. Not to worry, his hosts told him. Several had privately obtained Glock 17s and retrieved them from their lockers.

Walter took this as a promising sign: Some of New York's top in-house firearms trainers were curious enough about what he was selling to spend their own money on the gun, and in the process violate the ban on possessing a Glock within city limits. That summer, with the prohibition still in place, the Emergency Services Unit of the NYPD (what other cities call SWAT) quietly ordered 70 Glocks — another hopeful development.

In June 1986, the limitations of the six-shot revolver were illustrated in a gunfight in Queens. Rookie officer Scott Gadell chased a gunman, who opened fire on him. Gadell leaped for cover behind a stoop and shot back, emptying his .38-caliber Smith & Wesson. As he tried to reload, the gunman stepped forward and fired a fatal shot into the left side of Gadell's forehead. The gunman fired a total of nine shots from a nine-millimeter semiautomatic. "Every cop knows about Scott," a fellow officer later said. "He's an example of a cop who did everything he was supposed to but ended up dying because of second-rate equipment."

Then, in September 1988, the Associated Press landed a scoop that ricocheted around the city's media and beyond: New York Police Commissioner Benjamin Ward was carrying a Glock 17! "Police Commissioner Benjamin Ward is licensed to carry a controversial plastic super-pistol that is banned in New York City," the New York Post reported.

"'Super gun,' can you imagine?" Karl Walter would muse more than two decades later. "You can't buy that kind of attention, not for $50 million, not for $100 million."

A day after the Ward disclosure, the NYPD ended its Glock ban. A deputy police commissioner explained that research had demonstrated that the gun "could not be defined as an undetectable weapon, and in fact can be detected with today's present technology in the security field."

"From that moment on, everything started to roll," Walter said. Soon hundreds of NYPD narcotics detectives, organized-crime investigators, and other specialized units were carrying Glocks. The brand became one of three that New York authorizes, and about 20,000 of the city's officers carry a Glock.

After it won over New York, the ugly plastic sidearm from Austria was embraced by two thirds of all U.S. police departments. It has been glamorized in countless Hollywood movies, and featured as a ubiquitous presence on prime-time TV, rhapsodized about by hip-hop artists, and coveted by cops and crooks alike. It is the gun that protects us and the gun that hunts us, the weapon used by Jared Loughner to shoot Rep. Gabrielle Giffords and 18 others in Tucson. And Giffords herself told reporters in 2010, "I have a Glock nine-millimeter, and I'm a pretty good shot." For better or for worse, the Glock has truly become America's gun.

Adapted from Glock: The Rise of America's Gun. ©2012 by Paul M. Barrett. Published by Crown Publishers, a division of Random House Inc.