There is no national database of guns. Not of who owns them, how many are sold annually or even how many exist.
Federal law bars the Bureau of Alcohol, Tobacco, Firearms and Explosives from keeping track of guns. The only time the government can track the history of a gun, including its first buyer and seller, is after it's used in a crime. Despite calls for new limits on gun sales and stronger background checks, there is no effort afoot to change the way the government keeps track - or doesn't - of where the country's guns are.
When police want to trace a gun, it's a decidedly low-tech process. Charles J. Houser, who runs the ATF's National Tracing Center, says a routine trace can take about five days.