LAST February, Jim Zumbo, a burly, 66-year-old outdoors writer, got a phone call at his home near Cody, Wyo., from the rock star — and outspoken Second Amendment champion — Ted Nugent. “You messed up, man,” Mr. Zumbo says Mr. Nugent told him. “Big time.” Leland A. Nichols, left, an executive at Smith & Wesson in Springfield, Mass., and John Kapusta, an engineering manager, with an M&P 15 rifle. Such rifles have been crucial to the company’s turnaround plans. Two days earlier, Mr. Zumbo, a leading hunting journalist, outraged Mr. Nugent and many other gun owners when he suggested in...