Continuity mistake: Private Rich's left boot is totally black when he's put on the chopper. When it goes up, it's worn to the bare leather, and back to new looking during the landing.
Preventative Medicine - S7-E22
Continuity mistake: When Klinger enters Potters' tent, the bird alternates from about waist height to chest height between shots.
Continuity mistake: When Potter is on the phone, he turns to hush Hawkeye and BJ. As he does so, he's holding the receiver with his left hand, and covering the mouthpiece with his right. He then puts his left hand down on the arm of the chair. When the camera cuts in for a close up, his left hand is on the phone again.
Continuity mistake: Margaret comes in to the Officer's Club, and tells Klinger that the drinks are on her. He puts down two glasses, and starts to pour. When the camera cuts to a close up, he's just starting to pour into the same glass again.
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