Character mistake: As Potter and Hawkeye pull up to the MP checkpoint, Potter and the MP exchange salutes. As per Army regulations, no salutes are given under battle conditions. The reason is that if the superior officer, in this case Colonel Potter, returns the salute, he can be a target for snipers.
Character mistake: After Potter mocks Hawkeye for not hitting anything, Hawkeye replies "You fired as many shots as I did". In fact, Potter fired seven shots, Hawkeye only five. On a side note, this also suggests that Hawkeye probably was supposed to fire seven times, but his weapon jammed after the fifth shot. (00:22:00)