When Cowan is riding through the canyon at the start of the film he sees a
chukkar partridge on a rock. This could not happen in the post Civil War era, as this bird was not introduced into the U.S. from Afghanistan until the 1920's as a game bird.
They are using Winchester Model 1892 and/or 1894 rifles, which are recognizably different from the historically accurate Model 1873. This was common in westerns because those models were still in production when these movies were being made (until 1945 for the '92 and until 2006 for the '94), unlike the Model 1873, which ceased production in 1923.
Since the 1970s, historically accurate reproductions of the earlier firearms have been available from Italian manufacturers such as Uberti, Pedersoli, and Chiappa.
Since the 1970s, historically accurate reproductions of the earlier firearms have been available from Italian manufacturers such as Uberti, Pedersoli, and Chiappa.