The first thing that come to mind to me is someone who collects guns and studies the history of guns. What I do not understand is dimwits who call thugs who use gun for evil purposes gun nuts. Most of those thugs are not gun nuts they are just people who use guns to commit crimes. It is like calling someone who runs people over with a car as a car nut. Now I know there are people who fit my description of what a gun nut is that have committed crimes with guns, but the vast majority of times where someone commits a crime with a gun is is not by a gun nut.