Abstract: An indexer apparatus and method for using the indexer apparatus to prevent the unwanted migration or movement of a round within a chamber of a gun prior to firing. The indexer apparatus includes a movable member and a means for urging the movable member in the direction of a chambered round. The movable member may include a stud, a flexible or traverse section of a chamber or a barrel, a cam, and a ball bearing. The means for urging the moveable member in the direction of a chambered round include but are not limited to a spring, a solenoid, a magnet, a cam, an electromagnet, a valve, or a lever.