At least 20 manufacturers have shifted operations to states with friendlier attitudes toward firearmsSmith & Wesson CEO Mark Smith was fed up. He was running the largest firearms manufacturer in America, based in Springfield, Mass., where it had been making weapons since 1860, and yet state lawmakers were considering a bill to ban the manufacture of AR-15-style rifles for the civilian market. The proposed law would cripple Smith’s company. Sixty percent of Smith & Wesson’s revenue came from AR-15-style guns.So after years of flirting with the idea, Smith announced last September that Smith & Wesson was pulling up stakes and...