A Fistful of Dollars (1964)

Factual error: When the "U.S." soldiers open fire on the Mexican cavalry, they employ a machine gun. The only two rapid-firing weapons in that time period were the Gatling gun, which used a magazine or drum of rounds and was fired by turning a crank, or the "Mitrailleuse" volley gun, which required at least two men to operate it, one to load the ammunition blocks, and the other to turn, once again, a crank to fire the weapon. The gun pictured has a single operator and neither a crank, nor any visible cartridge feed.

Joe: When a man with .45 meets a man with a rifle, you said, the man with a pistol's a dead man. Let's see if that's true. Go ahead, load up and shoot.

Question: When they both finally grab their guns and load up and Joe spins the revolver, how's he so sure it's going to load that one live round?