What was full metal jacket about?

Answer 1

The first hour is about platoon 3192, a Marine infantry platoon being trained by Gunnery Sergeant Hartmann, a real-life former U.S. Marine. The second hour follows Private Joker, now Sergeant Joker, throughout his time in the Vietnam War.

Answer 2

This movie follows the experience of a marine recruit during the time of the Vietnam War. The central characters are recruits Joker, Cowboy, Gomer Pyle, and their draconian drill sergent Hartman. "Pyle" is hazed and while on the surface becomes a model marine he has really gone crazy. Just before graduation Pyle kills Hartman after Joker tries to help him in the bathroom. Pyle then commits suicide. Fast forward a year and Joker is in Vietnam as a correspondent. Joker becomes involved in the siege of Hue during the Tet Offensive. As part of this battles aftermath the squad he is leading confronts a merciless sniper that is in fact a young Vietnamese girl. After some debate, Joker kills her.