Continuity mistake: Jake and his prisoner arrive at the ranch where they find some dead killed by Indians. As they finish burying the people Jake's prisoner hits him with a shovel and then tosses it handle closes to him. When Jake wakes up the shovel is lying on the ground with the handle farthest away from him.
Factual error: The movie is set in 1843-44, when the rest of the world is still using cap and ball weapons, yet Ranger captain Jake Cutter is wielding a gunbelt with filled cartridge loops and a colt six-gun.
Factual error: The rifles that Jake Cutter has Paul Regret dig up are Henry repeaters, or possibly 1866 Winchesters. Either way weapons unavailable in the period depicted in the movie.
Visible crew/equipment: When John Wayne is on the wagon and the Comancheros are leading them to the secret hideout, for a split second in the background, a large truck and a trailer that seems to be camouflaged in the background are visible.
Revealing mistake: If you watch closely when the prisoner hits Jake with the shovel you can see the shovel bend as if it was rubber.
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.
Continuity mistake: When Jake Cutter and Paul Regret ride into the ranch yard, two of the victims are hanging upside down over the gate. In the close-up, there are three arrows imbedded in the gate posts. In the far shots, the arrows are not present.
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: Tully Crow dies with a model 1858 Remington New Model Army revolver in his hand, quite a feat in the year 1843.
Factual error: Melinda tells Paul Regret that her husband was killed 4 years ago, at the battle of San Jacinto. Since she is living in the year 1843, that battle would have taken place over 7 years ago.
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.