Continuity mistake: When Rambo fires the rocket launcher at the Russian Hind helicopter, he is clearly seen aiming a LAW rocket launcher. The LAW is fired by pressing a lever on the top. But when Rambo fires, a quick edit from a previous shot (on the patrol boat) shows him pulling a trigger from the Russian RPG launcher he used to dispatch the Vietnamese patrolboat earlier in the film. The film returns to show him holding the LAW rocket launcher again.
Factual error: When Rambo plays possum then suddenly takes out the Russian officer's Hind Helicopter he uses an M72A2 light anti-tank weapon (LAW). When fired, the M72A2 has a back blast that can kill out to 100 feet, which means he would have either blown up his own helicopter or killed all the MIA's he had rescued...
Character mistake: In the showdown scene between the Vietnamese officer and Rambo, the Vietnamese officer empties an entire magazine at Rambo from only about 20 metres away but only manages to hit the ground around Rambo's feet. What was he doing, aiming at his feet? He deserved to get blown up to bits for that effort.
Rambo: Wolf Den, this is Lone Wolf. Do you read? Prepare for emergency landing. Arriving with American POWs.