A Marine with 2nd Air Naval Gunfire Liaison Company performs a barrel change on the M2 .50 Caliber Heavy Machine Gun during a week-long field exercise at Camp Lejeune, N.C., Aug. 27, 2015. The Marines were conducting this training in order to uphold their readiness and standards in support of II Marine Expeditionary Force and to re-familiarize themselves with the weapons system. (U.S. Marine Corps photo by Cpl. Krista James/Released) - A Marine with 2nd Air Naval Gunfire Liaison Company performs a barrel change on the M2 .50 Caliber Heavy Machine Gun during a week-long field exercise at Camp Lejeune, N.C., Aug. 27, 2015. The Marines were conducting this training in order to uphold their readiness and standards in support of II Marine Expeditionary Force and to re-familiarize themselves with the weapons system. (U.S. Marine Corps photo by Cpl. Krista James/Released)