Ask him what his MOS was. This stands for “Military Occupational Status’’ in other words, what his job(or duty was). If he can’t answer that he’s a fraud. Also, ask what the duty(or job) of a Marine Gunerry Sargent is. A “Gunny’’ is unique to the Marine Corps, no other branch of the service has this rank. His job is to make sure all the Marines in his squad or platoon are fully supplied with ammo and that their weapons are clean, fully operational and ready for use at all times.
Try again. You can't test someone by making stuff up and having imprecise and incorrect answers yourself.
BTW...it's "Gunnery Sergeant".