Revealing mistake: Potter is taking the driving part of the test, with Rizzo riding along. In the long shot, as well as looking at Klinger stumbling along, you can see the Jeep occupants are stunt doubles.
Where There's a Will, There's a War - S10-E16
Revealing mistake: When Hawkeye injects the adrenalin into the chest of the dying soldier at the battalion Aid Station, you can see that he is actually injecting into a piece of rubber foam soaked with prop blood. (00:13:25)
Revealing mistake: During the conversation between Potter and Klinger in the Mess tent, if you look past them you can see Margaret loitering, waiting for her cue to enter.
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