X0306 4 2016-01-01 0 0000866121 ORBITAL ATK, INC. OA 0001045854 WEBSTER SCOTT L C/O ORBITAL ATK, INC. 45101 WARP DRIVE DULLES VA 20166 1 0 0 0 Common Stock 2015-10-28 5 G 0 2393 0 D 14480 I By Trust Common Stock 2015-10-28 5 G 0 2393 0 A 3336 D Common Stock 2016-01-01 4 M 0 2245 28.91 A 5581 D Common Stock 2016-01-01 4 F 0 727 89.34 D 4854 D Common Stock 2016-01-04 4 S 0 2519 88.8753 D 2335 D Director Stock Option (Right to Buy) 28.91 2016-01-01 4 M 0 2245 0 A 2007-01-03 2016-01-03 Common Stock 2245 0 D Shares withheld by the Issuer to satisfy exercise price. Sold pursuant to a Rule 10b5-1 trading plan adopted by the reporting person. This transaction was executed at prices ranging from $88.4897 to $89.46. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer, full information regarding the number of shares and prices at which the transaction was effected. /s/ Richard N. Osborne, Attorney-in-Fact 2016-01-05