Factual error: On several occasions during the film, one hears the sound effects of cartridges being ejected from revolvers, then reloaded. The revolvers carried by every character in the film appear to be of the "cap and ball" variety, which do not take cartridges and take MUCH longer to reload. Can't be the sound of the cylinder being removed - the cylinder in the closest revolver is visible throughout the sequence. In addition, several of the revolvers are Colts, which require a wedge and then the barrel to be removed before the cylinder can be changed. Only the Remington (which Eastwood carries) could have the cylinder swapped quickly enough.
Factual error: As Megan is holding her dead dog the camera pans back to Barret and over his left shoulder a jet trail is going across the sky.