Patzer

As Munny is getting beaten in the bar below, the Kid and Ned begin to flee the room. Ned falls out the window and rolls off of the wet roof and is heard landing in the mud on his back. When he jumps up, he's completely dry and not a bit of wetness, or mud/dirt on his back and arms.

When William Munny walks in and confronts the posse, his hat and clothes appear completely dry even though he has just come in from the pouring rain.

In the shot following W.W. Beauchamp's leak the planks are dry again with no puddle to be seen.

At the first time in the saloon, Munny pushes the glass on the table until it touches the bottle. The next shots show the glass a little distant from the bottle.

When given back his Spencer rifle by Bill, Ned's grip on the rifle jumps between shots.

The Schofield Kid's statement that he can "see well enough up to 50 feet" is presumably intended to mean that he is short-sighted. However, this is incompatible with such a condition, and there is no other medical condition that would result in good sight "up to 50 feet" and near-blindness at further distances.

English Bob says that no assassin would dare hold a gun to a monarch. There were, in fact, six assassination attempts made against Queen Victoria, and they were well known at the time. He certainly would have known about them. However, it should be noted that English Bob was mainly saying this to antagonize people and not necessarily because he truly believed it.

When seen from far away, it's obvious that the town of Big Whiskey is tiny, with fewer than a dozen buildings in the middle of nowhere. Yet the town has a sheriff with four or five deputies, most on duty at the same time.

Sheriffs are peace officers designated to patrol an entire county, not just a town. If Big Whiskey is the county seat of a large, sparsely populated county in Wyoming, they would need all of those deputies to police the various ranches and rural areas of the county.

On several occasions, English Bob pronounces his erstwhile biographer's name as "Boh'champ." As an Englishman, he would have known that Beauchamp is one the few names that have idiosyncratic pronunciations (such as 'Chumley' for Cholmondley, and 'Urkurt' for Urquhart). He should have pronounced it 'Beecham' (with a silent 'P'), especially as he reveled in illustrating his English superiority over his American colleagues.

A name is pronounced however the person who owns that name says its pronounced. If Beauchamp told English Bob that his name is pronounced "Boh'champ", then Bob is going to pronounce it that way regardless of how someone from England who has that name might pronounce it.

Several times during the film Ned Logan's Spencer is referred to as a rifle, when it is obviously a carbine.

A carbine is a type of rifle.

When English Bob is shooting the pheasants from the train, strings attached to the pheasants are clearly visible.

After Will and the Kid shoot the second cowboy and are riding away, the middle cowboy clearly fires shots in a different direction than the other cowboys, even though Will and the Kid are riding off in the same direction.

When Will, Ned, and the Kid first ride up to town and see English Bob in the train, Ned offers the Kid a drink. The Kid takes the bottle and clearly places his thumb over the top and drinks then his thumb can clearly be seen moving off the top after pretending to drink.

When William Munny wakes up from his fever after being assaulted by Little Bill, he sits outside the shack and talks to Delilah Fitzgerald. You can see the blue sky behind the house through springs in the wood revealing that it's not the same shack as in the first shot.

When William Munny is leaving the saloon after the gunfight, he shoots a wounded deputy on the floor with the Spencer rifle. However, after killing Little Bill in the previous scene, Munny hadn't used the lever of the Spencer with its characteristic sound to reload and then cock the hammer, as can be seen after he kneels down at the door of the saloon on his way out.

Set in 1880, when the townspeople are forming a posse, they are discussing who will pay for expenses, and one of them says that the store won't sell them any more 30-30 shells unless they pay cash. The 30-30 was not introduced as a cartridge until 1895.

Although pheasants were not introduced to the American west from Asia until the 1890s, they are present along the railroad tracks in 1880.

Several of the characters, including Little Bill and William Munny, are seen sometimes wearing shirts that button all the way up the front. This is incorrect for 1880, when men's shirts were still of the pullover variety, with or without a collar, and a small buttoned placket at the top.

The bottle of whiskey that the Kid drinks from contains the bottle's contents information embossed in the glass around the bottom of the side of the bottle. Bottles were not marked that way in 1880.

When Munny first shows up at Logan's home and Logan's wife can be seen regarding Munny's rifle, the rifle clearly has a molded plastic butt plate.

When the train first appears, the whistle blows while the locomotive is in the shot, but there is no steam blowing from the whistle.

In the bar room shootout scene, many pistol shots are fired. The Foley sound is correct. When Munny fires the rifle to kill Little Bill, the Foley sound adds the classic "rifle shot" sound, with obvious echoes. In the enclosed bar room, there would be no echoes of the shot, just a loud bang.

When Skinny comes to talk with Bill while he is building his house, you can see a light being reflected from an unknown source to the house.