Other mistake: When Kirby and the Sarge are in the helicopter during the big battle scene, when Kirby talks to Kowalski, you can see that Kirby's mouth is not matching what he says. Look closely because his hand blocks his mouth.
Other mistake: After one of Col. Kirby's soldiers has been killed he takes the dead soldier's M-16 and smashes it against a tree. Instead of a magazine the rifle has a plastic sound box, because the 'rifle' is really a toy made by Mattel.
Trivia: Even though the US military had a big part in the production of this film they asked the producer (John Wayne) not to credit them because they thought the movie was so pro-military that it bordered on propaganda.