At the end of the movie there is a fight and a pistol is knocked out of the hand of the bad guy. It clearly is an automatic shown lying on the floor. The bad guy retrieves the weapon and it is now a revolver. He even says at one point about having shot seven rounds and having one more left for Mr. X. The dialogue was appropriate for an automatic as was first shown and not the revolver someone replaced it with.
When Christine first visits the home of Alexis, she is abruptly sitting in a chair (from a standing position) when he first appears.
At the end, when the villain is shooting at Alexis, Alexis states he is out of bullets. He says, however, he has seven bullets, one in the chamber. He clearly has a revolver, and that does not have a chamber in the same way a pistol has. Although they exist, it is doubtful it is a seven-chambered revolver.
When Martin and the detective break up the séance, Martin explains to Christine that he has investigated her previous husband's (Paul) past. Instead of referring to the previous husband as "Paul", he refers to him as "Martin" (his own character's name).