Master Gunnery Sergeants are sometimes referred to by the nickname "Master Guns", "Master Gunny", or "Top". These nicknames are unacceptable in formal or ceremonial situations, and, at the rank holder's discretion, may also be unacceptable for use by lower-ranking Marines.
The Master Gunnery Sergeant insignia consists of a bursting bomb (colloquially referred to as a "pineapple" due to the similarity of its appearance as stylized) centered vertically between three chevrons and four rockers.
The grade was derived from another grade unique to the United States Marine Corps, the Gunnery Sergeant, and has been in use (though not continuously) since the time of the Spanish–American War (April 25 – August 12, 1898).
Establishment of the grade in its current form and paygrade occurred during sweeping reorganization of grades and paygrades in 1958 and 1959. The grade was included, along with the grade of Master Sergeant, in a new program for the paygrades of E-8 and E-9 which allowed senior SNCO billets to be filled by occupational specialists. This move was designed to officially acknowledge the ever-increasing complexity of modern warfare, while still maintaining the First Sergeant and Sergeant Major programs, with their historic command prestige. During and prior to World War II, this was reversed; the Sergeant Major was an administrative position while the Master Gunnery Sergeant was part of the S-3 section and enforced discipline.
Master Gunnery Sergeants (MGySgts) with an infantry Military Occupational Specialty (MOS) serve in the billet of Operations Chief, as the senior Staff Non-Commissioned Officer in the Operations Section of an infantry battalion, or higher level, headquarters. MGySgts with a non-infantry (e.g., artillery, tank, communications, logistics) MOS typically serve as either the Operations Chief of their MOS type battalion/regiment (e.g., artillery battalion/regiment, tank battalion) or as the section chief/NCOIC in their MOS related staff section (e.g., communications, logistics) at the regimental/Marine Aircraft Group, or higher level, headquarters. Master Gunnery Sergeants with an Aviation Maintenance MOS serve in the billet of Maintenance NCOIC/Chief in the Aircraft Maintenance Department of a Marine aircraft squadron.
In their annual performance evaluations, called "fitness reports", eligible Gunnery Sergeants indicate whether they wish to be considered for promotion to Master Sergeant or First Sergeant, and thus whether they enter the promotional track for Master Gunnery Sergeant or Sergeant Major. Once promoted, the promotional track is usually permanent, with lateral movement between the two programs very uncommon.
One of the major differences between the two E-9 grades is that Master Gunnery Sergeants retain their MOS, while Sergeants Major are given a new MOS to reflect their general command focus. This reinforces the Master Gunnery Sergeant's role as a provider of military leadership, technical acumen, and mastery of their MOS.