The Sisters Brothers (French title Les frères Sisters) is a 2018 co-production French-American Western movie directed by Jacques Audiard (his first English-language work) and starring John C. Reilly and Joaquin Phoenix as brothers Eli and Charlie Sisters, an infamous duo of gunslinging assassins in Oregon in 1851. The movie is based on Patrick DeWitt's novel.
The following weapons were used in the film The Sisters Brothers:
While Mayfield (Rebecca Root) doesn't use a gun in the film, promotional images show her carrying a revolver in holster. This is a compact gun in Colt 1849 Pocket style but the grip differs in size, allowing to guess that the holstered revolver is a "Wells Fargo" version.
Rifles
Sharps Carbine
John Morris (Jake Gyllenhaal) is armed with a Sharps Carbine during the shootout with Mayfield's Racoons. This is a modern replica of an original paper cartridge M1859 or M1863 versions (any of these models is anachronistic for 1851).
Sharps 1874 Gemmer
Charlie Sisters (Joaquin Phoenix) is seen with a Sharps 1874 Gemmer rifle, a version of the Sharps rifles family with the addition of some Hawken Rifle type parts, like the long ramrod below the barrel (on the breechloading Sharps it is used for cleaning the barrel).
Shotguns
Double Barreled Shotgun
Aged Mrs. Sisters (Carol Kane) holds a Double Barreled Shotgun when she sees two strangers near her house.