Alliant Techsystems agreed on Thursday to buy Bushnell Group Holdings, a top maker of gun accessories like rifle scopes, for $985 million in cash.

Bushnell’s ownership will move from the private equity firm MidOcean Partners to Alliant, an aerospace and defense contractor commonly known as ATK, whose businesses include making ammunition for both military and civilian firearms.

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“The Bushnell acquisition is consistent with ATK’s focus on establishing leadership positions in our core markets,” Mark DeYoung, ATK’s chief executive, said in a statement. “This acquisition will broaden our existing capabilities in the commercial shooting sports and expand our portfolio of branded shooting sports products.”

The deal is one of the first since the Newtown, Conn., school shooting, an incident that has put pressure on some owners of gun manufacturers to sell their holdings. Cerberus Capital Management, for example, is shopping the Freedom Group, which made the rifle used in the Newtown shootings.

Bushnell, on the other hand, does not make guns. But the 65-year-old company is one of the biggest makers of hunting accessories like binoculars and GPS systems, produced under brands like Bushnell, Primos, Uncle Mike’s and Serengeti. Based in Overland Park, Kan., the company has 1,100 employees.

“We are passionate about our brands, products and the outdoor enthusiasts we serve,” Blake Lipham, the chief executive of Bushnell Outdoor Products, said in a statement. “The opportunity to join the ATK family will allow us to further support the emerging needs of our customers and consumers.”

ATK, which plans to fold Bushnell into its accessories business, said it expects the deal to dilute its earnings in the 2014 fiscal year before becoming accretive the next year. ATK has secured $900 million in financing, and plans to use both new debt, an existing loan facility and cash on hand to pay for the deal.

ATK was advised by the law firm Cravath Swaine & Moore.