Staff Sgt. Steve Jervis, 363rd Training Squadron aircraft armament apprentice course instructor, watches as Airman Jarod Tracy, secures a retaining pin that holds the recoil cylinder on a 40 mm Bofors cannon. The Bofors is used by the AC-130u "Spooky" gunship for air to ground support. The recoil cylinder is responsible for ensuring a 7.8 inch recoil tolerance. Tracy and his classmates are scheduled to graduate on Oct. 17, 2017. (U.S. Air Force photo by Senior Airman Robert L. McIlrath)