X0306 4 2015-12-10 0 0000866121 ORBITAL ATK, INC. OA 0001188447 DEYOUNG MARK W C/O ORBITAL ATK, INC. 45101 WARP DRIVE DULLES VA 20166 1 0 0 0 Phantom Stock Units 2015-12-10 4 A 0 7.997 86.12 A Common Stock 7.997 2657 D Deferred Stock Units 2015-12-10 4 A 0 30.9142 86.12 A Common Stock 30.9142 10271 D These securities were acquired through the deemed reinvestment of dividend equivalents in the form of additional Phantom Stock Units of the Issuer (Orbital ATK, Inc.) credited to the reporting person's account under the Nonqualified Deferred Compensation Plan (NQDCP) of Vista Outdoor Inc. (Vista), a former subsidiary of the Issuer that was spun off as an independent company. The Orbital ATK Phantom Stock Units will be settled 100% in cash following the reporting person's termination of employment with Vista. 1-for-1. These securities were acquired through the deemed reinvestment of dividend equivalents in the form of additional Orbital ATK Deferred Stock Units credited to the reporting person's account under Vista's NQDCP. The Orbital ATK Deferred Stock Units will be settled 100% in shares of Orbital ATK common stock following the reporting person's termination of employment with Vista. Converts to common stock 1-for-1. /s/Mark W. DeYoung 2015-12-10