Visible crew/equipment: While Hoops Potter is going for the camp record in free throws, in overhead shots with everyone encircling the 'basketball court' - particularly right after free throw 28 and after Potter says that he feels like a sideshow freak, the boom can be seen moving around right beside the hoop's post at the top, left side of the screen.
Visible crew/equipment: While Hawkeye, BJ, and Charles are in the Swamp reading the letters, when BJ says, "Leave it to Charles to be the world's first poison pen-pal," the shadow of the boom mic can be seen moving around at the top right corner of the screen.
Visible crew/equipment: While BJ, Hawkeye, and Charles are in the Swamp, when BJ starts reading the letter from the child who thinks the army is like camping out Charles takes that letter away from BJ, and just as Charles is about to sit back down the edge of the Swamp set can be seen at the top right corner of the screen.
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