Revealing mistake: When Corporal Bin's group of men eventually arrive at Dunkirk, they speak to a soldier adding sandbags to a Vicker's gun position. Here (and later on in the film when it is shown firing) it has a blank-firing adaptor prominently fitted to the front. Additionally the belt of ammunition shown going through it is filled with blanks - no bullets project outside the other side to that of the actual cartridge cases.
Factual error: The Sergeant-Major of the artillery section Corporal Bins and his men are briefly attached to has two of his medal ribbons round the wrong way. He has up the Victory and British War Medal ribbons, when they should be worn BWM and then VM. A mistake an experienced senior NCO would not make.