Continuity mistake: When Radar is going to bed, he takes his shirt off and his upper body is naked. When he puts the blanket over his teddy bear you can see sleeves. Next shot, he is naked again.
Continuity mistake: Hawkeye is in the Swamp talking with Trapper. Hawkeye leaves and walks past the tent - Trapper is not inside. (00:07:30)
Continuity mistake: In the office, Radar is getting ready for bed, and has taken off his shirt. When he goes to tuck in his Teddy, he suddenly has sleeves.
Continuity mistake: During the inspection of arms, when Frank stands in front of the second soldier in line, the soldier's left collar is flipped up and his right collar is folded underneath his shirt in the shots facing him, but in shots facing Frank the soldier's entire collar is properly positioned.
Continuity mistake: As Hawkeye walks past the swamp after leaving Trapper, you can see the still is missing.
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