180218-N-ZU710-050 ATLANTIC OCEAN (February 18, 2018) Fire Controlman 2nd Class James Preston and Gunner's Mate 2nd Class Andrew Krempa performs maintenance on a MK38 25 mm machine gun following a live-fire exercise aboard the guided-missile destroyer USS Winston S. Churchill (DDG 81). USS Winston S. Churchill is underway as part of the Harry S. Truman Carrier Strike Group (HSTCSG) Composite Training Unit Exercise (COMPTUEX), which evaluates the strike group's ability as a whole to carry out sustained combat operations from the sea, ultimately certifying the HSTCSG for deployment. (U.S. Navy Photo by Mass Communication Specialist 3rd Class Michael Chen/Released)