Continuity mistake: In the part of the death of Cowboy, before he looks through the corner of the building to see the position of the sniper, there is a wall in good condition behind another wall which is broken. Later, when he goes back and starts to give orders, the wall that was in good condition is now broken without any reason for it to be and now the sniper can see Cowboy so she can shoot him. (01:39:20)
Continuity mistake: During the first firefight scene a soldier fires a M79 grenade launcher and hits one of the second-floor window. The glazing of the second window in the same floor is also destroyed. In the next shot the glazings of both windows are intact.
Revealing mistake: When the Marines are jogging through the training camp complex, singing "I don't know but I've been told..." you can see the British road junction markings on the tarmac underneath them. There is little evidence to suggest that there was any attempt to disguise or remove them.
Factual error: When 8-ball gets shot, in the shot which shows the platoon ducking near a wall with Cowboy, Joker and Animal Mother in the front, there are two weapon related errors. Cowboy's M-16 has a nickel (silver colored) firing assembly and Joker's M-16 has an A2 type pistol grip. The A2 types were introduced somewhere around the 80s, and nickel plated assemblies are rarely used (and were invented after Vietnam, too). The nickel assembly is visible at the beginning of the shot, and you can see the A2 grip when Joker is changing magazines (while Cowboy shouts cease fire).
Continuity mistake: In the scene where the sniper is shot, You can see blood on her face (especially on her upper lip) when she falls down after being hit, but when she lies on the floor afterwards, there is no blood on her face anymore.
Continuity mistake: During the graduation parade, if you look at the background you can see many large squad bay buildings with a few single trees in front of them, this scene seems to be shot at the actual Paris island. However when they show a close up of Joker's platoon in parade, the background changes to mostly trees, with only two or three small buildings behind them.
Continuity mistake: In the bathroom scene on the last night of boot camp, Pvt. Pyle is 'training' with a rifle. As he snaps to attention, the shot from behind shows him with legs slightly apart, a second later the shot from the front shows him with his legs perfectly together, yet he never moves.
Continuity mistake: When the tanks are moving into the city with the Marines i.e. after meeting Private Cowboy, Animal Mother and the rest, they run into a firefight. When they stop shooting and are reloading watch the leader's ammo clip. It's missing in one shot of him, in the next he's ejecting the magazine and putting in a fresh one before shooting the two Vietnamese with it.
Continuity mistake: After Cowboy is hit by the sniper Animal Mother fires wildly and destroys part of the "My Toan" sign. A few seconds later you can see it is intact.
Continuity mistake: When Joker and Rafterman are in transit on the chopper, we see the gunner firing out the cargo door. We can see out the cargo door that the ground is pretty far away, the chopper is obviously pretty high up in the air, so high that if there were people down on the ground it would be rather hard to see them. However the camera switches to the gunner's point of view shooting at people, and the chopper only seems to be about 20 feet off the ground.
Continuity mistake: After Lt. Touchdown has been shot, behind the tank, he falls to the ground with his rifle still grasped in one of his hands but when the marines move in to aid him his rifle has vanished.
Revealing mistake: When Private Pyle shoots himself you can see that the blood splatters from the side of the screen instead of going straight back from the back of his head.
Factual error: Joker would not have been allowed to go through basic training and out into the field with wire-rimmed glasses. He would have been issued plastic/cellulose-framed Regulation Prescription Glasses (AKA BCGs or "Birth Control Glasses") like Private Cowboy's.
Continuity mistake: When Hartman punches private Joker you can see Hartman swing with his left hand in one shot and a split second later (angle from the floor) when Joker has been struck, Hartman's right hand has made contact and is pulling back.
Revealing mistake: In the early latrine scene when Privates Cowboy and Joker are mopping the floor, the mops they are using are dry. As they dip each mop into the bucket, there is no water dripping. When they move the bucket, the sound indicates it is empty, as anyone who has ever used a mop & metal bucket could validate.
Factual error: The film is set in and around 1968. In one scene, a copy of Ursula LeGuin's novel "The Word for World is Forest" is seen at Joker's bedside. This novel was not published until 1976.
Continuity mistake: When Joker is talking to the colonel about his peace badge, it is there at the beginning of the conversation, but then disappears when Joker turns his back to the camera. It then reappears in the next scene when he is walking along with Rafterman.
Factual error: At one point Joker is doing chin ups, with Hartman motivating him. Joker does three chin-ups, but not a single one of them was done properly. You're supposed to lock your elbows all the way out on the way down, and your chin needs to clear the plane of the bar. Joker never locks his arms out, barely gets over the bar. In reality Hartman would have been all over him about this, drill instructors are notoriously strict about proper technique.
Other mistake: When the sniper fires her rifle at Joker after his rifle jams, she fires at him and strangely no shell casings are ejected. A few bursts later and her rifle does eject shell casings.
Continuity mistake: When Joker goes to see Cowboy and the squad are sitting in the temple, the dead Vietnamese's face can be seen without the hat covering it. When the photo is taken by Rafterman, his hat appears and is removed.
Chosen answer: A Drill Instructor is always mad at the recruits in order to forge discipline. Private Pyle was the biggest screwup in the unit, thus creating more work for him.
Captain Defenestrator