I know he was a Marine, but he was also a recruiter in at least one episode.
IIRC, they made his uniform accurate, complete with Korean combat insignia.
They didn't make him a hokey TV uniform.
E-7 Gunnery Sergeant Vince Carter. And he was also an actual former Army Sergeant serving in WW2 making 14 beach assaults in his time in service. I guess that's why he was a natural for his roll LOL.
In the show he was first Gomer's Drill Sergeant or DI {ducking for cover for getting the name wrong LOL} in Boot Camp and to Carter's horror afterward following Boot Camp Gomer was permanently assigned to his unit afterward.