For all the attention that is placed on the nation’s estimated 300 million firearms, most guns rest in cases, drawers and safes. Few are holstered. Few get used to actually stop a threat. Even armed soldiers and police officers often go entire careers without firing a shot on duty, reported the St. Louis Dispatch.For many, self-defense is the leading argument for gun ownership rights. It’s also the primary motivation for keeping a firearm, now surpassing even hunting, according to a recent Pew survey.Data on the incidents of guns’ being used in self-defense vary widely from study to study. But only...