If the Walmart is still in business, you call it. The actual store. Not corporate headquarters, or some warehouse, but the actual Walmart in Omaha or Miami or Wheeling. You call that store and you say, “To whom did you sell this Taurus PT 92 with this particular serial number on it?” By law, every gun dealer in America has to keep a “bound book” or an “orderly arrangement of loose-leaf pages” (some have been known to use toilet paper in protest) to record every firearm's manufacturer or importer, model, serial number, type, caliber or gauge, date received, date of sale. This record corresponds to the store's stack of 4473s, which some clerk has to go dig through in order to read you the information from the form. Or he can fax it.

Congratulations. You have found your gun owner. “I get a sense of ‘Yeah, I got you, pal,’ ” Hester tells me, about what it feels like to find just the right 4473. It can take people at the tracing center 70 phone calls on one trace alone. There are rows and rows of cubicles filled with ladies on phones doing the calling, but not everything happens by phone. They do have some Internet in the building: e-Trace is a system that allows cops to submit requests for gun traces and get the results back by computer, if they're subscribers. They can also mail the requests in. Either way, once you have found the name of the gun owner, you get back to the cop who initiated the trace.

Happiness Is a Found Gun Linking a killer to his gun is preposterously hard. On purpose. — Rachel Wilkinson Cops nab a gun. Now what?

Police contact the tracing center and describe the gun they've got: the make, the model, etc. Tracers call the gunmaker...

And have the manufacturer (say, Glock or Smith & Wesson) dig up the retailer they sold it to.

Then find the gun store...

Tracers phone Walmart (or wherever), and there, a guy hunts down a form signed by the gun buyer.

But the gun store closed!

A shuttered retailer's forms go to the tracing center (almost 2 million monthly).

So tracers comb their files

To find the gun owner, they hunt by hand for the form he signed back when he first bought the gun.

“And then I say, ‘Okay, your trace is done; I got the buyer,’ ” Hester tells me. “And they say, ‘Oh, who is it?’ ” Maybe it's one of the suspects. “And he'll say, ‘Are you sure?’ And I'll say, ‘I've got this form in my hand here. I'm looking at the form. I can tell you for a fact right now the purchaser and possessor are the same person.’ And without exception, these guys are like, ‘Oh, man, you're a rock star. You're a god. Man, you rule.’ ”

But hang on, because maybe you didn't get so lucky. Maybe you're working on a trace, and it turns out that the Walmart that sold the gun was one of those old cruddy Walmarts that closed down in the 1990s. This leads you back, as almost everything does, to Charlie's boxes.

Now you go dig.

All the out-of-business records that come in here—2 million last month—are eventually imaged and organized according to the store that sent them. It might be 50,000 Form 4473s from one Dick's Sporting Goods in some suburb of Cleveland. So, say you need to find one particular 4473 from that store. “We go through them,” Charlie tells me. “Just like photographs from your Christmas party, and we look through every one. Until we find it.”

More than 30 percent of all traces lead investigators here, hand-searching through boxes, or going frame by frame on microfilm readers, looking for a 4473 from Mom and Pop Gun Shop long after Mom and Pop closed up shop.

“It's in here somewhere,” Linda Mills tells me. I meet her in the “roll room,” a cavern of beige drawers you pull out and pick among—40,000 rolls of microfilm in all, each with about 10,000 frames on it. “I'll find it,” says Mills. She's in her 70s and due for retirement and wears her white hair long and down her back. She's looking for the record of a person who bought a Remington 870 12-gauge shotgun that was sold by a now defunct dealer in Denver. She thinks she picked the right roll, so she carries it back to her desk, where the lights are as dim as a closet's, and where a microfilm reader circa 1973 is planted. Here she will sit, as she has for the past 18 years, turning a dial right while countless images zoom past.

“I'm looking for a W,” she says. The images are the color of asphalt, and the writing on them looks like tiny pebbles, and they whiz by so fast, I begin to get actual car sickness. I ask her how she can possibly read anything moving this fast.

“I'm looking for a W,” she says, picking up a magnifying glass and leaning in toward the upper left of the screen. She's hunting for the first letter of a 15-character code atop the defunct dealer's record books. “Sometimes they'll just put the numbers, they won't put the alphabet.” Now she's squinting, one eye closed, the machine whirring, the images zooming. “We had 8's. We're still in the 9's. See, now it went on to a different gun again…. But if we get past—wait!”

Abruptly, she hits the “stop” button. “See, here's W's.”

To search the millions of records they have on file, tracers must scroll through miles of old microfilm.

Information Is Power

Sixty-five percent of the time, workers at the tracing center are able to successfully trace a gun used in a crime back to the original purchaser. A routine trace takes about a week, but they can turn an “urgent” around in 24 hours. The San Bernardino case was an urgent. The Boston Marathon bomber case was an urgent. Gabby Giffords: urgent. Charleston. Aurora. Fort Hood. Columbine. Washington Navy Yard. Sikh temple. Just figure every crime you ever watched endless horrifying footage of on TV involved somebody here in Martinsburg searching through a rat's nest of records and then experiencing a moment of jubilance upon seeing that, yes, this is it, here is the 4473 that belongs to that lunatic. (Or his mother. Or his uncle. Or the pawnshop dealer who sold it to someone else. Tracing the gun beyond the initial point of purchase is on the cops.)

This is the maddening, inefficient way gun tracing works, and there is no effort afoot to make it work any better. For all the talking we do about imposing new limits on assault weapons, or stronger background checks, nobody talks about fixing the way we keep track—or don't keep track—of where all the guns are.

On just one of the days I visited the tracing center, there were 5,000 trace requests in the hopper awaiting attention. There would be about a thousand more the next day.

In 2013, recognizing how important tracing is for solving crimes, and for providing intelligence regarding patterns of illegal gun trafficking, President Obama asked for more of it: He signed a memorandum demanding that all firearms recovered in the course of criminal investigations be traced.

But Congress didn't give Charlie any funds, or manpower, to accommodate an influx. In fact, his budget has been flat since 2005. What Charlie got from Congress is the same thing he always gets: scrutiny. “If a stick drops in the road, we're getting some pressure,” he tells me. The idea—which is forcefully pushed by the gun lobby and implanted in the heads of lawmakers at the behest of the NRA—is to make sure Charlie is not using his power to access America's 4473s to secretly create a searchable database.

There is no other place in America where technological advances are against the law. Unless you count the Amish. Even if a gun store that has gone out of business hands over records that it had kept on computer files, Charlie can't use them. He has to have the files printed out, and then the ladies take pictures of them and store them that way. Anything that allows people to search by name is verboten.

To be clear: Charlie doesn't want names. “You got a dead guy in Chicago, right? So what name did you want me to look for?” he points out. “I ain't got a damn clue! Nobody else does, either. I don't need to be able to search by the name. If I knew the name, I wouldn't have to trace the gun.”