Second time that’s been said on this thread. Was he promoted at retirement?
IIRC, he was given the gunnery Sgt "promotion" as an honor by the Corps after his movie career and first TV show. He was a Corps sergeant, just not gunny grade.
Ermey was medically retired as a Staff Sergeant in 1972. The Commandant bestowed the title of Honorary Gunny upon him as a PR move in May of 2002. That “promotion” carries as much weight as the “promotion” of Gomer Pyle to Lance Corporal by the same Commandant, James Jones, in August of 2001.