Visible crew/equipment: While BJ's holding Peg's letter and telling Hawkeye about being homesick and depressed, the edge of the Swamp set can be seen at the top, left corner of the screen.
Visible crew/equipment: After Radar shows the box of bees to BJ and Hawkeye, when BJ gets in the jeep and drives off, just before the shot cuts away we can see the T-mark on the ground at Radar's feet.
Visible crew/equipment: After a 14 hour shift in the OR, when sleepy BJ and Hawkeye are in the change room just as Hawkeye says, "Let's face it, their demand is bigger than your supply," the shadow of the moving boom mic is visible on the curtain.
Continuity mistake: When BJ and Hawkeye are peeking into Radar's box of bees, in the wideshot there's tape on the box, but in the closeup the tape has vanished.
Visible crew/equipment: As the M.P. jeep escorting the General's jeep gets close to the camera, a reflection of a lighting rig or reflector is seen in the right windscreen.
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