Revealing mistake: In the Gatling Gun scene when the camera cuts to a short couple frame shot showing a closeup on the .45-70 Government ammunition casings on the ground that are falling from the gun, the casings are star crimped. Star crimped casings indicate blank ammunition. Standard ammunition isn't possible with star crimping. The size and casing shape indicates .45-70 Gov which was popular in these guns at this time. (01:46:40)
Revealing mistake: When Ransom and Hallie Stoddard are riding the train back to Washington at the end of the film, pay attention to the view out the window as Hallie responds to Ransom's suggestion of returning to Shinbone. When the conductor brings the spittoon and talks to them, the same exterior footage repeats from when Hallie started to speak. (02:01:30 - 02:02:15)
Revealing mistake: The first time we see the artillery blow up a group of Confederate soldiers, the guys wear pretty distinctive hats; the one at the center has a red band on it, the one to his right a straw hat, etc. Ten seconds later, the artillery blows up another group of soldiers...who are the exact same group from before. It's just another take. (00:00:30)
Revealing mistake: When the children stay with the tribe, all of the horses being ridden, although shown having a saddle blanket, actually have saddles under those blankets.
Revealing mistake: When Buck and the gang ride away from the saloon in Dallas where JC made a few new 'friends', the footage is sped-up for a second just as soon as James Caan jumps on his horse. (00:05:50)
Revealing mistake: At the beginning of the opening title sequence if you look behind Silence as he rides through the snow covered forest you can see what looks like a couple of skiers whizz by. (00:05:34)
Revealing mistake: During "Many a New Day", when Laurie sings "many a red sun will set" and before they all hear the Cummings girl laugh outside, Laurie and two others are looking into a mirror. The actresses are actually looking into the camera through a mirror frame, to give the illusion that we are seeing their reflections. When the girl with the long black hair joins them, you see her run in from the side, then her "reflection" in the mirror. However, if it was a real mirror, you wouldn't see her run in from the side. (00:44:00)
Revealing mistake: During the bison shooting scene, a bison goes down close to the camera and both horns jiggle like they're about to fall off. Looks quite fake.
Revealing mistake: The gang's visit to Northfield, Minnesota reveals a typical late 18th century town, with dozens of people on many horses and horse drawn wagons. All the horses leave deep tracks in the dirt, because they are walking on freshly laid soil that has not had time to compact. There is absolutely no horse manure to be seen anywhere, despite dozens of horses. Clearly, the film makers used a 20th century town and laid new soil over the pavement shortly before the filming began.
Revealing mistake: When Cactus is ran over by the train, one can see he is held with several security straps.