Sergeant Major Barnett enlisted in the Marine Corps on 29 August 1990. He came on active duty and attended Recruit Training on 3 July 1991 and graduated from Kilo Company, Third Recruit Training Battalion, Parris Island, South Carolina on 21 November 1991. After graduating Recruit Training, he completed Marine Combat Training at Camp Geiger, North Carolina. He then attended and graduated from the Ground Radio Maintenance School with the assigned Military Occupational Specialty of 2841, Ground Radio Repairman. He then reported to Bravo Company, 4th Light Armored Reconnaissance Battalion in Frederick, Maryland. While serving with Company B, he held billets as a Ground Radio Repairman, Communications Chief, and Platoon Sergeant respectively.
In February of 2003, Sergeant Barnett reported to Career Management Team, Headquarters, Marine Corps. While serving with Career Management Team he held the position of Career Counselor, assisting with promotion board preparation and reenlistment requests. He was promoted to the rank of Staff Sergeant March of 2005.
During the month of September 2006, Staff Sergeant Barnett transferred to Personnel Retrieval and Processing Company (-), 4th Marine Logistics Group in Washington, D.C. While there, he served as the Company First Sergeant.
In April of 2007, Staff Sergeant Barnett transferred to the Marine Corps Liaison office at the National Naval Medical Center in Bethesda, Maryland. While there, he served as the Staff Non-Commissioned Officer in Charge for the Individual Mobilization Augmentee Detachment.
In March of 2008, Staff Sergeant Barnett returned to Personnel Retrieval and Processing Company (-), 4th Marine Logistics Group in Washington, D.C. Upon his promotion to Gunnery Sergeant in June of 2008, Gunnery Sergeant Barnett served as the Platoon Commander for 1st Platoon.
Gunnery Sergeant Barnett mobilized in December of 2009 with Personnel Retrieval and Processing Detachment in support of Operation Enduring Freedom 10.1. In January of 2010, along with the detachment, he was attached to Headquarters and Service Company, 1st Marine Logistics Group (Forward). Gunnery Sergeant Barnett held the position of Mortuary Affairs Collection Point Staff Non-Commissioned Officer In Charge at Camp Bastion in the Helmand Province of Afghanistan.
Gunnery Sergeant Barnett accepted orders March 2011 in order to attach to 3d Marine Division in support of Operation Tomodachi. At the conclusion of those orders in April 2011, he returned to Personnel Retrieval and Processing Company (-) and assumed the responsibilities of Company Gunnery Sergeant.
In December of 2011, Gunnery Sergeant Barnett assumed the responsibilities of Company First Sergeant of Personnel Retrieval and Processing Company (-), 4th Marine Logistics Group in Washington, D.C.
Effective August 2012, First Sergeant Barnett was assigned as the Company First Sergeant of Bravo Company, 4th Combat Engineer Battalion, 4th Marine Division.
In October of 2014, First Sergeant Barnett was selected to return to active duty with Enlisted Professional Military Education, Marine Corps University at Marine Corps Base Quantico.
Sergeant Major Barnett was promoted to his current rank May 2016. He continues to serve with Enlisted Professional Military Education at Marine Corps Base Quantico.
Additionally, in September 2016, Sergeant Major Barnett assumed the responsibility as the Battalion Sergeant Major of 3d Battalion, 25th Marine Regiment, 4th Marine Division.
Sergeant Major Barnett’s personal awards include: the Navy and Marine Corps Commendation Medal with gold star in lieu of second award, Navy Marine Corps Achievement Medal and the Outstanding Volunteer Service Medal.