Visible crew/equipment: After Harper, the JAG, has Trapper and Hawkeye sign and attest to the blood report, when Radar enters Henry's office we can see a crewmember's hand near the floor between the two doors, preventing the closing door from swinging back and forth. (00:22:20)
Visible crew/equipment: While Radar is in Henry's office with the woman and her baby, being teased by Trapper and Hawkeye about the possibility of him being the father, just as Frank walks into the office a crewmember's hand can be seen between the two doors near the floor, preventing the closing door from swinging.
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