Firearms line the shelves in the gun library at the U.S. Bureau of Alcohol, Tobacco and Firearms National Tracing Center in Martinsburg, West Virginia

Firearms line the shelves in the gun library at the U.S. Bureau of Alcohol, Tobacco and Firearms National Tracing Center in Martinsburg, West Virginia

Firearms line the shelves in the gun library at the U.S. Bureau of Alcohol, Tobacco and Firearms National Tracing Center in Martinsburg, West Virginia December 15, 2015. The guns represent many of the models the ATF has come across in their investigations, and are collected through seizures from criminals or donations from manufacturers and members of the public. REUTERS/Jonathan Ernst – RTX254TZ