Factual error: Lucas is wearing a pair of jeans with a large "W" stitched on the right back pocket. These are Wrangler jeans, which first went on sale in 1947. "The Rifleman" is set in the 1880s.
Factual error: The rifle model which the rifleman used was manufactured in 1892, but the film takes place in 1881.
Factual error: Lucas is constantly twirling the rifle after rapid firing a few shots. Since the cocking ring is set on semi-automatic, the rifle should fire as it comes around.
Suggested correction: He twirls the rifle in the opening of the show, after he's just emptied it completely.
The original comment doesn't state the beginning of the show. This does happen throughout the series.
Factual error: Ralph Hayden hires Mario Rosati to kill Lucas McCain, who had shot and wounded Hayden many years before. Hayden says McCain previously lived in Enid, Oklahoma. "The Rifleman" is set in the 1880s and Enid did not exist until 1893. (00:01:10)
Factual error: Lucas and Mark are traveling on what is said to be the first train to ever reach the town of North Fork. The episode is set in the 1880s and the train shown was part of the M.K. & T. Railroad, which at that time was operating only in Missouri, Kansas, Texas and Oklahoma. The fictional town of North Fork is located in New Mexico Territory.