This article or section is for a series that is Ongoing, or currently on the air and thus is a continuous work in progress. Screencaps may not be immediately available and information may not be up to date.
Many variations of the Single Action Army revolver are used in the series.
Single Action Army Artillery Model (5.5" barrel)
Teddy Flood (James Marsden) carries an Artillery Model with a 5.5" barrel. A similar revolver is used by Craig ([[(Currie Graham) in "The Original" (S1E01).
Single Action Army Cavalry Model (7.5" barrel)
The Cavalry Model with a 7.5" barrel appears to be the revolver that is used by Dolores Abernathy (Evan Rachel Wood) in the series.
Remington Model 1875
The Remington 1875 revolver is used by some of the characters in Westworld.
LeMat 1861
The Man in Black (Ed Harris) carries what appears to be a LeMat 1861 revolver, which is proven to be a customized cartridge-firing model rather than a percussion black-powder weapon. The Man in Black is seen reloading his revolver by breaking the weapon in half (the barrel and cylinder assembly from the frame), showing that the pistol has a cartridge cylinder similar to those produced by reproduction companies such as Uberti and Pietta (While this type of conversion wasn't existent in the Old West, this series takes place in a futuristic theme park. That being said, this conversion isn't technically an anachronism). The Man in Black loads the revolver with what appear to be .38 Short Colt cartridges, as well as a long, brass shotgun shell (appears to be around a 20 gauge) in the underbarrel shotgun. He is then seen firing the revolver on the normal cylinders, but also flipping the switch on the hammer and firing the shotgun.
Also, interestingly enough, it appears that The Man in Black carries an entire second barrel/cylinder assembly in a holster mounted on his belt behind the holster for the full pistol. While the purpose of this has not yet been demonstrated, it can be assumed that it is meant to be a quicker reload.