Continuity mistake: At the onset of the movie, the chopper Braddock and his team are in is shot down over a lake and they have to bail. Each of the five men on board jumps and then their name is listed followed by a "Missing In Action" stamp on the screen. However, if you look closely in the chopper before they all get ready to bail, you will see another guy in the back with a hat on (and it is not Opelka, Franklin, or Nester) who wasn't supposed to be there. It looks a lot like one of the other Americans who was presumably killed in the firefight prior to the chopper arriving to pick up the remaining survivors, taking off and then being shot down.
Revealing mistake: At the beginning of the film when Nester and Opelka and at least two other Americans are attempting to run towards the chopper, you hear a series of Vietnamese mortars which hit two of the Americans, followed by screams. If you look real closely at the last mortar to hit the second American, it is a scare-crow type figure dressed in military fatigues that takes the mortar hit.
Factual error: When Col. Yin threatens to execute Cpl. Opelka, he draws a semi-automatic handgun, racks the slide and hands it to a subordinate. The subordinate puts the gun to Opelka's head and pulls the trigger but nothing happens because the pistol isn't loaded. He racks the slide again and puts the pistol back to Opelka's head and Opelka looks terrified as again the trigger is pulled and nothing happens. This is a mistake because if there were a round in the magazine the first time the slide was cycled it would have been chambered. If the weapon wasn't loaded the first time it was cycled, they could have cycled it all day long and it wasn't going to chamber a round. And a Special Forces soldier like Opelka would have known that.
Factual error: Almost throughout the whole movie, US soldiers wear full on camouflage. The army didn't wear camouflage in Vietnam, they only wore solid green uniforms.