There are several firearms throughout the mini-series that should not be there as they didn't exist at the time. Bigfoot Wallace was using a Remington model 1858 rifle, but as the model name indicates that rifle was not available until 1858, Dead Man's Walk takes place in 1842. Several people, including Captain Salazar and Gus, are seen using Colt Walker revolvers, but they were not available until 1847.