In this high-tech age, authorities seeking to connect guns with killers remain stuck in the last century.
At the Bureau of Alcohol, Tobacco, Firearms and Explosives' Tracing Center, the firearms reference vault holds more than 12,000 weapons, ranging from AK-47s to an anti-tank cannon.
Federal law enforcement try to help local police solve crimes, matching guns and tracing where they were bought. It is a complicated task made more difficult because agents must conduct business the old-fashioned way: by hand.
"The number-one problem we have with tracing is properly identifying a firearm," said Charlie Houser, the tracing center's chief. "All these different guns, a lot of them look exactly alike but they are not alike. There are some subtle differences in each one."
While a buyer's background might have been checked by the FBI, the only record of sale is a gun dealer's paper form. The records are kept in attics and basements, where they can be vulnerable to flooding and even fires.
"We get out about 1,000 to 1,200 boxes of these a month," Houser said, referring to boxes of firearm receipts from licensed gun dealers.
A half-billion paper records are transferred to microfilm or now scanned into digital images. The information is never entered into a computer system.
The inefficiency of such a labor-intensive antiquated system has cost taxpayers an estimated $60 million in the past 12 years.
"When people are visually going through microfilm, searching through 60,000 pages of information for a single gun, they can miss it," Houser said.
A trace takes about five days. If it was computerized, however, it would take just hours.
The ATF is banned from being more efficient because members of Congress, backed by the National Rifle Association, passed laws forbidding the agency from using computers that can read the content of the forms, thus creating a national registry.
Iowa Republican Sen. Charles Grassley, who was instrumental in passing the laws, said he found the reasoning behind not computerizing the forms "legitimate."
"Now, is that the best way to solve a crime?" he said. "I don't think I'm prepared to make a judgment on that at this point. I do know, under the Second Amendment, I don't want the government registering guns. I don't want the government knowing who's got a gun and doesn't have a gun. … There might be a better way."
As for the $60 million in the past 12 years, Grassley said Americans must "go out of our way to protect constitutional rights in this country."