Continuity mistake: As the discussion about Burns draws to a close, Potter starts to grab the files on his desk. As he says "Dismissed", he grabs them again.
Continuity mistake: From the back, Potter is facing directly at Hawkeye and BJ. From the front, he's in quarter profile, left side forward.
Continuity mistake: As BJ mentions fingernails on a chalkboard, Potter hunches his shoulders up. A second later, after the angle changes, he repeats the action.
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