Factual error: Tully Crow dies with a model 1858 Remington New Model Army revolver in his hand, quite a feat in the year 1843.
Factual error: While giving Jake and Regret a tour of his hideout, the comanchero leader points out his powder mill, claiming that he gets his nitrates from his own mines, and the saltpeter from deposits to the south. If he has nitrate mines, he has no need of saltpeter.they are the same ingredient for black powder, potassium nitrate.
Factual error: Jake questions a prisoner who was recently released from Yuma Territorial Prison, a prison that would not have been constructed until 1876, 33 years in the future. As a matter of fact, the area where the town and prison would be built was, at the time period of the movie, still part of Mexico.
Factual error: After Regret is sworn in as a Texas Ranger, he and Jake head out in the wagon with Tobe as a scout. Tobe pulls out a pair of binoculars to survey the route, but in 1843, binoculars were not yet invented.