Continuity mistake: During the scene where the Joker moves into the building to kill the sniper, the sniper sees him and starts shooting at the pillar he is behind. During this shot, large chunks of the pillar fall away, but in the next shot, when the sniper gets shot, the pillar is intact.
Continuity mistake: In the opening scene, Gunnery Sgt. Hartman is making his speech and passes by Privates Cowboy and Joker on his way to the other side of the barracks. On his way he passes Private Pyle standing to the right of Private Joker. Later in the scene, when he rushes over to confront Private Joker and then moves on to Private Cowboy and then Private Pyle, Private Pyle is on the left of Private Joker.
Continuity mistake: In the fire fight in the city near the end of the film, one of the men is firing a M-16 around a corner. As the camera angle changes he is seen firing left handed and right handed. Back and forth several times. Also in the same sequence the magazine in his gun keeps vanishing. One shot he has it and in the next there is no magazine in the gun and yet he hasn't moved.
Continuity mistake: When D.I. Hartman dumps the contents of Private Pyle's footlocker on the floor, in the next few shots the layout of the clutter on the floor changes. Note that after Hartman confronts Pyle with the jelly doughnut and turns away, there is a clear path through the clutter for Hartman that disappears in subsequent shots.
Continuity mistake: Pvt. Pyle is on the rifle range with Gunnery Sergeant Hartman right behind him. When filmed from Pyle's right side, he is wearing a white wrist wrap/brace but the shot moves behind him and it is gone. Back to the right side and it reappears.
Continuity mistake: During the drill scene when Sgt. Hartman is asking Private Pyle if he knows the difference between his left and his right, watch the positioning of Pvt Pyle's cap. After being struck the first time, the cap is slightly cocked. After the shot returns to Pyle and before he gets struck for the second time, the cap is obviously cocked further over.
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: 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 "blanket party" scene, Pyle appears to be sleeping on two (wrinkled) pillows. When Cowboy covers his mouth Pyle is sleeping on one very neat pillow.
Visible crew/equipment: When Cowboy, Joker, Rafterman and the other Marines are running across the buildings to get to Animal in the final sniper scene, watch the foreground. If you freeze the movie right as they reach Animal, you can see they run by a boom mic and a crew member. A bicycle is also there (just to help you out).
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: There's a scene where Sgt. Hartman goes to punch Pvt. Joker in the stomach. If you look carefully, he starts to punch with his left, then we instantly see Joker getting punched by his right.
Continuity mistake: When Gomer Pyle is in the toilet with his rifle and after shooting the drill instructor, Pyle sits down on the fourth toilet seat from the back of the room. In the next shot where Pyle kills himself, he is sitting on the third toilet seat. You can see this already from the front shot of Pyle when he kills himself because there is a rise in the wall next to the third seat, which is visible through the whole scene. It is more obvious in the following shot where you can see the row of toilet seats and Pyle sitting dead on the third one.
Other mistake: When the GI's 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.