The gun used by just about everyone in the film is the Single Action Army revolver in various barrel lengths and calibers. Many look to be in far too good condition to be the guns of Frontiersman and have obviously newer color case hardening as evidenced by the fact that it isn't worn in the slightest. During the 19th century, they used Cyanide to harden the color case, unaware of how unsafe it was to use. Today, more conventional and longer lasting methods are used. It is likely these guns were supplied by Aldo Uberti Inc., a major manufacturer of replica 19th century firearms. Due to the extreme frequency of these guns' appearances in the film, there are a lot of screenshots for them.
Sheriff John T. Langston (John Cleese) uses an Enfield Mk II revolver, the predecessor to the Webley, as his sidearm in the film. As an English character, played by an English actor, it's appropriate that he carries an English revolver.
When Paden (Kevin Kline) tries to buy a gun in the gun store, several Single Action Armies are seen in the glass case, but one of the guns is a Remington 1875.
"Slick" Calvin Stanhope (Jeff Goldblum) keeps a Remington 1866 Derringer hidden in his sleeve and does a neat trick to flip the gun out, instantly readying it for use.
When Paden (Kevin Kline) runs into the gun-shop to buy a gun to kill the man who stole his horse, his lack of money leaves him with a worn-out Webley No.5 revolver which comes apart when first handled. The gun has an Adams patent ejector instead of the standard fixed rod. This would have been necessary for the shot where the cylinder falls out when the ejector rod is opened - the revolver would have been assembled without the cylinder arbor pin installed, thereby leaving the cylinder free to fall when the ejector was opened.
Winchester 1866 "Yellow Boy" (mocked up as Henry 1860)
Malachi "Mal" Johnson (Danny Glover) uses a Winchester 1866 "Yellow Boy" rifle mocked up like a Henry 1860 by removing the fore-end. The dead giveaways are the loading gate on the receiver and the lack of a magazine tube slit and spring follower under the magazine tube. It is rather strange that he would use this fake Henry when his father uses an actual Henry rifle in the movie.
It's believed that this was done so Danny Glover didn't have to deal with the spring guide handle sliding into and pinching his finger while firing multiple rounds, multiple times during filming.
Ezra Johnson (Joe Seneca), Mal's father, uses a Henry 1860 rifle with an engraved receiver. When murdered by some of Cobb's thugs, the gun is used by one of them until he is killed by Emmet (Scott Glenn). Emmet then uses the gun when preparing for a fight, shooting the prickers off a cactus plant. The rifle is then given to Mal and he uses both the Henry and his fake Henry (made from a Winchester 1866 rifle) during the gunfight at the ranch.
Both the Rifle and Saddle Ring Carbine versions of the Winchester 1873 rifle are seen used by several characters in the film, most notably Emmet (Scott Glenn) and Paden (Kevin Kline), who both keep the rifles as saddle guns.
A Colt Model 1878 is seen used by several extras in the film.
Error creating thumbnail: File missingColt Model 1878 - 12 Gauge.Error creating thumbnail: File missingAn assassin at the start of the film falls through the shed ceiling with his Colt Model 1878 shotgun, which somehow lands on top of him despite how his firing it means it would be under him. No reason to complain though, it gave us a clear shot of the gun.Error creating thumbnail: File missingThe bartender tries to shoot Mal with his Colt 1878 shotgun but gets whacked with a statue.Error creating thumbnail: File missingWhen Cobb's thugs attack the town member's party, they throw torches into the buildings. One member shoots a torch out of the air with his Colt 1878 but gets shot for his good deed.
J. Stevens & Company 1878
The two coach drivers who rob the waggon train keep a J. Stevens & Company 1878 shotgun with Indian decorations on the stock as their weapon.
