Shares of ammunition maker Vista Outdoor Inc. /zigman2/quotes/205852373/composite VSTO +4.47% sank 4.7% in afternoon trading Tuesday, after Walmart Inc. /zigman2/quotes/207374728/composite WMT +1.30% said it was halting the sale of some rifle ammunition that can also be used in military-style weapons. Walmart also said it would sell through its handgun ammunition and will end handgun sales in Alaska, which will mark the retailer's complete exit from handguns. Vista's stock selloff comes after the stock had ended August with a 27% gain in 11 sessions, since it closed at a record low of $4.41 on Aug. 15. The stock has now shed 53% year to date, while Walmart's stock has run up 23% and the Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA +1.05% has gained 12%. Walmart also said the remaining assortment of guns it will sell will be "even more focused on the needs of hunting and sport shooting enthusiasts," such as long-barrel deer rifles and shotguns, and much of the ammunition they require. The company expects the moves will reduce its market share of the ammunition market to about 6% to 9% from 20%. Shares of other gun makers also declined, with Smith & Wesson parent American Outdoor Brands Corp. losing 2.8% and AR-556 autoloading modern sporting rifle maker Sturm Ruger & Co. /zigman2/quotes/200036418/composite RGR +3.43% slipping 0.7%.