Among the main findings of these research studies are: (1) New guns are recovered disproportionately in crime;11,13,16–18,22 (2) Some licensed firearm retailers are disproportionately frequent sources of crime guns; these retailers are linked to more guns traced by ATF than would be expected from their overall volume of gun sales;24 (3) Under test conditions, significant proportions of licensed retailers and private party gun sellers will knowingly participate in illegal gun sales;25,26 (4) On average, about one third of guns used in crime in any community are acquired in that community, another third come from elsewhere in the same state, and a third are brought from other states;11,13,16–18,22 (5) There are longstanding interstate trafficking routes for crime guns, typically from states with weaker gun regulations to states with stronger ones. The best known of these is the “Iron Pipeline” from the Southeast to the Middle Atlantic and New England.11,13,16–18,22