The ocean doesn't move on the beach scene revealing it to be a painted back drop.
The floor at Briggs' hotel where Colonel Shtemenko goes to kill the Professor is continuous from the hotel desk to the elevator revealing it is not a real elevator as there would be no way for it to move.
There is a significant difference in weight between a loaded gun and an unloaded one (actually - 112 grams for the weapon used in the movie, as declared by its manufacturer). It is unlikely for a professional killer to overlook it.
An experienced assassin would be able to tell from the weight that the bullets had been removed from a gun.