Re: Their part in his downfall
"Sgt asks if anybody has fired one before."
Reminds me of the possibly apocryphal scene in the comedy film "Carry On Sergeant" (1958) - which is set just after WW2.
The sergeant is giving a lecture to the new conscripts about maintenance of a submachine gun. Having stripped it to a collection of components he notices that one guy is obviously not paying attention.
So the offender is told to put it back together - which he does with amazing speed and dexterity. The sergeant apologises for thinking him inattentive. The soldier admits he wasn't listening - but says his previous job was in the factory that made the gun - doing the final test assembly.
It was a very slick demonstration in one continuous take by Bob Monkhouse. He must have had a lot of practice.