Never saw the movie, but in the trailer I agree it looks like an M1. Lot of times in movies (more with rifles than handguns), they'll have to manually operate a semiauto's action due to firing blanks without a blank adapter. What was weird was that he was operating that M1(?) from the left side of the receiver. There may be some ambidextrous attachment for M1's; I don't know that much about them.