When Slim is surrounded by Creighton and his gang, Josh points a rifle at him and yells, "There's a 30-30 pointed at your head Creighton." The 30-30 was not invented until 1895, some 20 years after the setting of this show. When the camera focuses on the bore of the rifle, it is obvious that it a much larger caliber weapon, probably a 44 Henry, a very popular weapon at that time.