Every time somebody pulls the trigger on a gun, it leaves distinctive marks on the bullet or cartridge case. Police have long used those tell-tale marks to help them link a gun to a crime, and bullet-matching is a regular feature of police dramas like CSI. In recent years, some lawmakers and gun control groups have pushed for a national database that would record the ballistics signature of every gun sold in the United States. But a new report from a prestigious... (GunPolicy.org)