Not realistic, overrated
FMJ is a boot camp movie, not realistic at all to the Vietnam war.
They never made it into the jungle, or even into Asia! It was shot in cold England, in a 6-7 story warehouse district, while Hue was a lush tropical 2-3 story city.
Kubrick never had a planned ending and it fails. He even asked the actors how to finish the movie, hence the dumb mickey mouse ending.
R Lee Ermey was so disappointment in Kubrick's direction he made his own Nam' flick Siege Of Firebase Gloria, much more realistic.