Continuity mistake: Charles (in scrubs), Radar, and Father Mulchahy are all in the changing room when Radar and Mulchahy go take a phone call. When entering the comm room, Charles has appeared and is complaining about waiting for a phone call in his fatigues.
Continuity mistake: While Igor is serving dinner, his cap peak goes from being up in the front shot to down in the side shot, while he is talking to Col. Potter.
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