Factual error: When Radar, Hawkeye, and BJ find the letter from cpl. Benson to I Corps, Radar says that cpl. Benson's been here since June. Later in the episode when col. Potter, Radar, Hawkeye and BJ confront Benson, Benson says he is there on orders of a colonel who did not get treated quickly enough. Potter says he remembers this colonel was there a couple of months back. BUT, this episode of M*A*S*H takes place during Kentucky Derby Day. The Kentucky Derby has always been held the first Saturday in May. So, if Benson has only been at the 4077th for two months, and he arrived in June, then this episode should be taking place in August, not May.
Factual error: Charles mistakenly injects a Post Op patient with curare instead of morphine. This would have been hard to do. Curare was not approved for use in Korea by the U.S. Army and it would not have been there. Even if it had been, curare was used in conjunction with anesthetics in the operating theatre. It would make no sense to have it in the Post Op. (source pg. 14 "Notable Names in Anasthesia" by J. Roger Maltby, Royal Society of Medicine - Great Britain). (00:12:20)
Factual error: Radar's mother's boyfriend owns a Nash Metropolitan, a car that was not produced until after the end of the Korean War.
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator