From Halopedia, the Halo wiki
Master Sergeant, abbreviated to MSGT, is a Enlistment rank of E-8 in the United Nations Space Command Unified Ground Command (UNICOM) rank structure. It is preceded by Gunnery Sergeant, it is equal in grade to the command career track First Sergeant, and a subordinate to a Master Gunnery Sergeant and a Sergeant Major.[1]
Division administration.[1]
Master Sergeant is in the technical career track and directly leads onto the E-9 rank Master Gunnery Sergeant.[1]