Revealing mistake: When Herod shoots Rusty in the back before the final gunfight, a car can be seen driving down the road in the background.
Revealing mistake: In the scene at the end of the movie where Lee Marvin is running interference during the escape by shooting in the air, horses pulling a beer wagon get startled and run into the street where the wagon turns over. At the beginning of the shot, when the horses begin to bolt, you can see the stuntman driving the wagon. He is sitting low behind the wooden front of the wagon (which has holes cut in it so he can see out).
Revealing mistake: When The Deputy Charley Rakes goes to Cricket's house and attacks Jack, you see Charley throw Jack down the steps outside the house. If you look closely, you can see he lands on something really soft and spongy like a mattress which is hidden under the foliage on the ground to break his fall. When Charley walks down the steps towards Jack, you see him walk on it, which again looks really soft and spongy.
Revealing mistake: After the trailer explodes on the bridge, towards the end the truck swerves to the left. As it drives off the bridge there is no tail shaft between the gearbox and front diff - the truck falling off the bridge is just a shell.
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: In the scene where the boy is shot in the leg and the carried away by an unionist soldier you can see more union soldiers storm past them. The bayonets of the soldiers are obviously made of rubber as they are dangling while the rifles are moved up and down by the running soldiers.
Revealing mistake: The caboose and two bunk cars are uncoupled and sent rolling down the hill, with troops locked inside. As the cars roll off a cliff, troops can be heard yelling. However, as the cars hit the ground and shatter into rubble, the wood does not appear to be blood stained, nor does there appear to be any sign of bodies in the debris. The cars were obviously empty for the scene, and given the circumstances of the soldiers allegedly trapped within them, it's unlikely that any of the soldiers could've gotten out in time.
Revealing mistake: When we see a wagon with a woman and several children in it, the horses get spooked and run. A woman is seen desperately trying to stop the runaway horses. In the next scene you can see the children are not real and the woman is a man dressed in a woman's dress, obviously a stunt man used for that scene.
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 Bud and Wes take competitive turns riding the bull at the presumed high speeds, the bucking patterns and timing aren't consistent. A few times either man goes less than 15 seconds on a mid speed rather than full on bucking. Which even for a practice doesn't add up, and wouldn't fly during a competition.
Revealing mistake: Near the end of the movie, the Bunch are relaxing and passing around a bottle of whiskey. While the actors could not be expected to drink real alcohol, it's too bad the prop guy could not have mixed up some less foamy instant tea, typically used as a substitute in these scenes.
Revealing mistake: When Potter starts shaving at the morning of the Indian attack on the wagon train, his mirror falls off the post, and as he bends down to retrieve it, an arrow embeds itself right above his head. If you look closely in that scene, you can see a length of targeting wire used to guide the arrow sticking to the post above Potter's head. (00:37:10)
Revealing mistake: At the end after the driver of the wagon has fallen off and the horses are running wild you can see a slot in the front of the seat and arms holding the reins.
Revealing mistake: Many of the cavalry soldiers were carrying M-1 Garand rifles (WW2 era rifles).
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 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: During Cactus Jack's first trap failure while he's under Handsome's wagon, Jack loses his cowboy boots and pants. The camera follows the insane stretching suspenders, and when it cuts to Cactus Jack in his red long johns, the black booties for the stunt are visible at his feet/ankles; then next wide shot, that footgear is gone. Additionally, as Cactus Jack gets pulled toward his pants, it appears that he slides past his pants in the long shot, but is successful in the next close-up. (00:33:00)
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: When Caleb is running for the van (during the motel shootout) there is a dramatic moment when he is shot in the back and is in pain. As he goes to wrap the blanket around himself you can see an orange tube leading underneath his clothing above his pants. Presumably this tube is pumping the smoke to simulate burning. (00:59:44)
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)