First Sergeant McCullough enlisted in the Marine Corps on 5 July 2005, and attended recruit training at MCRD San Diego, CA. Upon graduation on 10 September 2005, Private First Class McCullough attended Infantry Training Battalion in Camp Pendleton, California.
After completing MOS School, Private First Class McCullough was assigned to Company A, 1st Battalion, 5th Marines, 1st Marine Division as a Squad Automatic Rifleman. In 2006, Private First Class McCullough attended Assault Climbers Course. In July 2006, Private First Class McCullough deployed with the 31th Marine Expeditionary Unit (MEU) as a part of Battalion Landing Team, 1st Battalion, 5th Marines as a Squad Automatic Rifleman. In 2008 Lance Corporal McCullough deployed on the 11th (MEU) as a part of Battalion Landing Team, 1st Battalion, 5th Marines as a Team Leader. Corporal McCullough attended Corporals Course on the USS Cleveland in 2008. Once Corporal McCullough returned from the 11th MEU he attended the Martial Arts Instructors Course. After completing the course, Corporal McCullough attended Infantry Squad Leaders Course.
Upon graduating Infantry Squad Leaders Course, he was promoted to Sergeant. Sergeant McCullough then deployed to Afghanistan in 2009 as a Squad Leader in support of OEF 0-9. During the deployment, Sergeant McCullough became the Platoon Sergeant of 1st Platoon, Alpha Company. After the deployment, Sergeant McCullough was selected to be the Joint Unit Multipurpose Platoon (JUMP) Commander for 1st Battalion 5th Marines. In 2010 Sergeant McCullough attended Infantry Unit Leaders course, and upon graduating, Sergeant McCullough deployed in 2011 to Sangin, Afghanistan in support of OEF 1-1. During that deployment, he was meritoriously promoted to Staff Sergeant while serving as JUMP Platoon Commander. After deployment, Staff Sergeant McCullough attended Career Course in 2012.
Staff Sergeant McCullough received orders to SOI West, serving as an Advanced Infantryman Course Squad Instructor from September 2012 to October 2013, taking over as the Chief Instructor through July 2015.
Staff Sergeant McCullough reported to 1st Battalion 5th Marines in July 2015, where held the billet of Platoon Sergeant in Charlie Company 3rd Platoon. After returning from the 31st MEU in 2016 Staff Sergeant McCullough became the Company Gunnery Sergeant for Company C. On September 1, 2016, he was promoted to Gunnery Sergeant and deployed on the 15th MEU. In January 2018 Gunnery Sergeant McCullough attended Advance Course at Staff Academy West. In May 2018 Gunnery Sergeant McCullough attended Basic Security Guard School. In August 2018 Gunnery Sergeant McCullough checked into Company B, MCSFBn Kings Bay Georgia. March 2020 to October 2020 Gunnery Sergeant McCullough served as the Orientation SNCOIC.
On 1 October, First Sergeant McCullough was Frocked and received orders to Company A, 1st Battalion, 24th Marines Battle Creek Michigan where he currently serves as the Inspector Instructor First Sergeant.
First Sergeant McCullough's personal awards include the Navy and Marine Corps Commendation Medal with three gold stars in lieu of fourth award, Navy and Marine Corps Achievement Medal with combat distinguishing device, and Combat Action Ribbon.