The Fastest Draw (1966)

Amos Handworthy's grandfather was quick on the draw: as a U.S marshal, it was a job requirement if you wanted to stay alive. But now Amos has built a gun-slinging robot, programmed to be a split second slower than him in a gunfight, so that he can perpetuate the myth and glory of his grandfather's frontier past. But will Amos bet his life on a duel with real bullets?