Continuity mistake: At lunch, when Frank is getting his own back against Hawkeye, in the long shots of the table the plate of bread is beside Henry and in the closeups it is in front of Trapper. (00:11:30)
Other mistake: When Hawkeye walks into the shower tent while Ugly John's showering he removes his robe, and just as Hawkeye swings open the door to step into the shower stall we can see that he's wearing something, presumably a swimsuit.
Continuity mistake: In the mess tent, after Radar uses the ketchup he puts the cap back on, but while Hawkeye and Trapper tease Radar about his hearty appetite, when it cuts to Radar's closeups the cap is off the ketchup, but then it's back on in the wideshot.
Continuity mistake: After the opening credits it cuts to Hawkeye, Trapper, Radar, and Ugly John playing poker in the Swamp and they're all wearing their uniforms when they run out to the incoming choppers, but what we see next is the same footage from the Pilot that's shown in the opening credits, with Hawkeye and Trapper wearing Hawaiian shirts as they meet the choppers.
Continuity mistake: In the storage tent, between wide shots and close ups, the rank insignia on Blake's hat goes from centered to over his right eye and back a few times.
Continuity mistake: In the mess tent, when Frank asks Hawkeye why he makes his life so miserable in the OR, notice that in the wideshots there's a silver pitcher, napkin holder, etc. On the table between Trapper and Margaret who are facing each other, but in the shots facing Margaret and Frank, and also Trapper and Hawkeye all of those things vanish and then reappear.
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