Visible crew/equipment: After Radar walks into the Swamp and gives Hawkeye and Trapper the coffee and case folders, just as Radar tells them that he was too sleepy he walks out, and the actor's chalk T-mark can be seen on the ground (although faint, it's distinguishable).
Factual error: The Logan Ramsey character tells Hawkeye and Trapper that with enough notice he could get them anything, even a B-52. The first B-52A entered service in 1954, a year after the Korean War ended.
Continuity mistake: As the boys talk to Col. Lambert, Trapper is back a bit from the table. When the angle changes, he's a lot closer.
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