Lance Cpl. Zachary Miller, a motor vehicle operator with 2nd Light Armored Reconnaissance Battalion, 2nd Marine Division function checks a Mk-19 automatic grenade launcher during a Machine Gunners Course at the Division Combat Skills Center aboard Marine Corps Base Camp Lejeune, North Carolina, April 15, 2015. During the course the Marines were trained how to properly disassemble, reassemble and maintain the M249 squad automatic weapon, the M240B machine gun, Browning M2 .50 caliber machine gun and the MK19 automatic grenade launcher. (U.S. Marine Corps photo by Pfc. David N. Hersey/Released) - Lance Cpl. Zachary Miller, a motor vehicle operator with 2nd Light Armored Reconnaissance Battalion, 2nd Marine Division function checks a Mk-19 automatic grenade launcher during a Machine Gunners Course at the Division Combat Skills Center aboard Marine Corps Base Camp Lejeune, North Carolina, April 15, 2015. During the course the Marines were trained how to properly disassemble, reassemble and maintain the M249 squad automatic weapon, the M240B machine gun, Browning M2 .50 caliber machine gun and the MK19 automatic grenade launcher. (U.S. Marine Corps photo by Pfc. David N. Hersey/Released)