X0306 4 2018-05-17 0 0000866121 ORBITAL ATK, INC. OA 0001276303 MARTINEZ ROMAN IV C/O ORBITAL ATK, INC. 45101 WARP DRIVE DULLES VA 20166 1 0 0 0 Phantom Stock Units 2018-05-17 4 A 0 18.2836 133.28 A Common Stock 18.2836 7633 D These securities were acquired through the deemed reinvestment of dividend equivalents in the form of additional Phantom Stock Units credited to the reporting person's account under the Issuer's Deferred Fee Plan for Non-Employee Directors. The Phantom Stock Units are to be settled 100% in cash after the reporting person ceases to be a director of the Issuer. 1-for-1. /s/ Richard N. Osborne, Attorney-in-Fact 2018-05-17