In the opening scene labeled as being set in 1871, a pair of Colt Peacemaker revolvers with 4-3/4 inch barrels is shown. This model was developed for the US Army in 1873. Civilian sales started in 1875, and the 4-3/4 barrel length wasn't available until 1877.
In the final shootout, Books fires his belly gun four times, before he drops it, and his holster gun three times. The two nearly simultaneous shots through Sweeney's table are so fast, they have to be one from each pistol. After Gillom takes the holster gun and fires it three times at the bartender, it should be empty. But as he prepares to throw the gun away, it is obvious there are still loaded rounds in at least two chambers.
After Books and Gillom practice shooting at a tree, they go for a walk. Gillom pulls out a whiskey bottle. In the cut just before Books takes the bottle from Gillom's hand, the bottle position changes from Gillom's left hand to his right hand. The level of the whiskey in the bottle changes as it is handed back and forth between Gillom and Books.
Towards the end of the movie, before the final gunfight, Sweeney drives up and parks his automobile outside the Metropole. As he gets out of the auto, he raises the tiller. Moments later when Books arrives at the Metropole, the tiller on Sweeney's auto is in the lower position.
After he discharges Dobkins setting a foot on his buttock, and Dobkins stretchs out on the ground, Books throws away his hat which falls on his feet. When Dobkins picks it up still lying, it is on his right side almost about his hip.
As Gillom walks to the door when leaving the bar after covering Books, his shirt is buttoned to the neck. When he is next seen after exiting the bar outside, the top of his shirt is clearly unbuttoned.
In the final shoot-out the mirror behind the bar is real at the beginning and up to the first shot when it shatters. Thereafter it is replaced by something which is obviously not mirror glass and which punctures rather than shatters.
When Sweeney is coming at Books with the table in front of him, the squib detonation wires are visible on the floor. The same wires are seen when Books falls to the floor after being shot by the bartender, and when Gillom shoots the bartender the second time.
Pulford kills the gambler with a shot through the heart that covers the length of the saloon. Such a wound should have only resulted in a relatively small amount of blood. Yet, when he hits the floor, he is literally covered with blood down to his legs.
When Bond and Books first meet, Books tells Bond that his name is William Hickock, former marshal of Abilene. Bond tells Gillom what Books said, and Gillom tells her that Wild Bill Hickock died before he (Gillom) was born. Wild Bill Hickock's name was James Butler Hickock, not William Hickock.
Books' gun is a six-shooter, but during the climactic gunfight in the Metropole Saloon, it miraculously fires 8 bullets: 1 at Cobb, 3 at Sweeney, 1 at Pulford, and finally, Gillom picks it up and fires 3 to kill the bartender.
When Gilliam picks up Books gun after the bartender shot him, there is red on the end of the barrel, apparently Books blood. When Gilliam shots the bartender, the red is still visible on the end of the barrel, but when he throws the gun away, there is no red on the end of the barrel.