Acting in Full Metal Jacket

First of all, I would like to say I liked the movie Full Metal Jacket. One main reason is that it exposes, as Joker said, a dualism in humanity. This dualism is about the lack of distinction between what’s fair and right.
The character I've selected for my analysis of the movie’s acting is Leonard "Gomer Pyle" Lawrence, played by Vincent D'Onofrio. I believe this actor was a very good choice for this role. One main reason is that the character's traits went very well with the actor's strengths. At first, he was playing the role of a stupid person who didn't know anything at all, and that couldn't follow either the instructions given by Gunnery Sergeant Hartman or the other soldiers in their training. He fitted the physical requirements perfectly for this role. He is a heavy man, and I think he can really portray an idiot very well. But he can also make a psychopathic face. The character this actor performed changed completely at some point in the movie. He changed from being a stupid soldier to a psychopathic one.
I believe these kinds of changes in the character's personality, interests, and emotions are very difficult to perform, even by a famous actor. I think Vincent D’Onofrio performed it pretty well. He really looked like a psycho killer in the character's second "phase". He absolutely convinced me about the character's change.
Kubrick selected this movie's actors with discernment. Acting in this movie help made the audience feel the reality that, in all its aspects, soldiers had to live before and during wars.