I just watched the film tonight, in fact. Robards is good as Doc Holiday, but I felt Garner was miscast as Earp. Unable to turn on his signature charm, he’s relentlessly grim in the part. Garner would play Earp again about twenty years later, in the flawed, but enjoyable Sunset. There, much more of his charm is on display. Some sources claim that director John Sturges wanted DeForest Kelley to reprise his role as Morgan Earp in Hour of the Gun (he had played the part in Sturges’ The Gunfight at the O.K. Corral in 1957), but Star Trek meant he was unavailable.