What’s funny is that Lee Ermey hadn’t even been hired to play the role of Gunny Sgt. Hartman.
For one thing he wasn’t an actor... he had been hired as a consultant to teach a real actor how to be a DI... which resulted in a videotape of Ermey shouting obscene insults non-stop for 15 minutes.. Kubrick saw that and hired Ermey instead.
There’s also the rumor that Ermey had asked for the role and Kubrick said no- at which point Ermey barked “Stand up when you’re spoken to!” and Kubrick instinctively obeyed. And that got him the role.
Good decision by Kubrick. His performance made the film.