From his desk, Ryan Busse could hear his boss ranting that the country’s largest gun manufacturer, Smith and Wesson, had betrayed its peers in the industry. Just a year after the 1999 mass shooting at Columbine High School in Colorado, Smith and Wesson had reached a settlement with the White House agreeing to a slew of safety measures, including trigger locks on all its new guns. Now other gun makers — including Kimber America, which employed Busse — would surely be pressured to do the same. The National Rifle Association’s Institute for Legislative Action accused Smith and Wesson of “craven...