Gun maker Sturm, Ruger & Co. posted an unusual loss during the fourth quarter, dragged down by a $41 million charge related to the termination and settlement of the company’s defined benefit pension plan that Ruger had flagged earlier would depress its bottom line. At the same time, Ruger said gun sales were again lower in the fourth quarter than prior year levels, reflecting an industry-wide slowdown following exceptionally robust sales throughout 2012 and 2013. Firearm sales, particularly of handguns, have slowed nationally after President Obama was unable to push through new gun-control legislation. But now, after cutting production levels...