If you've ever watched a crime show, you've probably wondered how law enforcement was able to figure out the exact weapon used in a crime. That's easy: they probably have the same one. The FBI keeps a collection of more than 7,000 firearms spanning 80 years inside the FBI Laboratory in Quantico, Virginia.

The gun collection is used to compare firearms and other samples in active investigations with virtually every handgun and rifle known to man. As John Webb, a firearms examiner in the Lab's Firearms/Toolmarks Unit, tells FBI.gov: "Often, an investigator will receive a part of a firearm or a firearm that isn't functional. We can take that and compare it with our reference collection, determine what isn't functioning, and repair it so we can obtain the test fires we need to conduct examinations with bullets and cartridge cases."