In the pilot episode "Deadwood" (S1E01), Byron Sampson (Christopher Darga) leads his lynch mob to Bullock's jail armed with a Henry 1860 (specifically, his is a steel frame, rather than the usual brass).
Sharps 1874
A Sharps 1874 rifle is seen being sold on a rack above a Sharps carbine in "Suffer the Little Children" (S1E08). In "Jewel's Boot is Made For Walking" (S1E11), a Sharps is seen hanging on the wall in Cy Tolliver's office in the Bella Union.
Sharps 1874 Cavalry Carbine
A Sharps 1874 Cavalry Carbine rifle is seen being sold on a rack below a Sharps 1874 in Suffer the Little Children (1.08).
Springfield 1873 Trapdoor Carbine
When they arrive in Deadwood in "Sold Under Sin" (S1E12), General Crook's Cavalrymen carry Trapdoor Springfield 1873 Carbine rifles.
Winchester Model 1866 "Yellow Boy"
One of Tolliver's men at the Bella Union fires a Winchester Model 1866 "Yellow Boy" into the air to celebrate and announce its official opening at 8:00 p.m. in "Reconnoitering the Rim" (S1E03). In "The Trial of Jack McCall" (S1E05), Tom Nuttall (Leon Rippy) places a Model '66 inside "Wild Bill" Hickok's casket.
Winchester Model 1873
Many characters carry the Winchester Model 1873 throughout the series, including several anonymous prospectors and townspeople. Charlie Utter (Dayton Callie) pulls a Model '73 from his saddle bag when he sees Bullock beaten by the Indian in "Plague" (S1E06).
Shotguns
Rossi Overland double-barreled shotgun
In the pilot episode "Deadwood" (S1E01), both Seth Bullock (Timothy Olyphant) and Sol Star (John Hawkes) wield Rossi Overland Coach Guns with exposed hammers to keep the lynch mob away. Dr. Amos Cochran (Brad Dourif) also grabs one when defending Sofia Metz (Bree Seanna Wall) from Swearengen's men in "Deep Water" (S1E02).
Handguns
Colt Single Action Army
Many characters carry and use Single Action Army revolvers throughout the show.
Charlie Utter (Dayton Callie) carries a Single Action Army Artillery Model with a 5.5" barrel throughout the series. Jack McCall (Garret Dillahunt) uses an Artillery Model during the confrontation with "Wild Bill" Hickok in "Here Was a Man" (S1E04). According to contemporary reports, the real Jack McCall had used a double-action .45 caliber revolver to murder Hickok, but this an error, because there were no .45 caliber double action revolvers that existed in 1876 (the year Hickok was murdered). This error is often made by people who have very little or no knowledge of firearms. The reason this mistake was made is because a person (like a newspaper reporter) who is not familiar with firearms would refer to a single action as a double-action, because one must cock the hammer on a single-action before they can pull the trigger - which is two "actions" - thus this mistake is made. In
"Sold Under Sin" (S1E12), several Cavalry soldiers and a man assisting Con Stapleton use Artillery Model SAAs.
Sheriff's Model
In the pilot episode "Deadwood" (S1E01), a gun salesman seen while Seth Bullock rides into town showing off a Colt Sheriff's Model Single Action Army with a 3.5" barrel.
Colt 1860 Army (Richards-Mason Conversion)
Dan Dority (W. Earl Brown) has a Colt 1860 Army (Richards-Mason cartridge conversion) as his main sidearm throughout the series. In the pilot episode "Deadwood" (S1E01), Ned Mason (Jamie McShane) carries a Colt Army.
Colt 1851 Navy
James Butler "Wild Bill" Hickok (Keith Carradine) carries a matched pair of ivory-handled Colt 1851 Navy revolvers until his death in "Here Was A Man" (S1E04). During "Reconnoitering the Rim" (S1E03), Hickok is playing a game of poker with Jack McCall (Garret Dillahunt) in Nuttall's No. 10 saloon when he is down to his last eight dollars, putting one of his Colt Navy's on the table to bet it. McCall tells Hickok that his Colt is worth at least $40 more than his raise, putting up $50 more if Hickok will place both guns on the table. This prompts Hickok to quickly draw his other Colt Navy, scaring the other players, until he puts it on the table with his other, winning the bet with a flush of clubs.
Colt 1851 Navy (Richards-Mason Conversion)
When Calamity Jane (Robin Weigert) draws and re-holsters her revolver on Doc Cochran in the pilot episode, it is a Colt 1851 Navy with a Richards-Mason cartridge conversion. When the scene is shown from her POV, she has her regular SAA Cavalry Model. The shots of Jane with the Colt Navy are a continuity error.
Colt New Line
After Trixie places her derringer on Swearengen's nightstand in the pilot episode, he wakes up the next morning (in the episode Deep Water (1.02)) and picks it up, asking if it was "for him". However, a continuity error occurred and the pistol became an .22 caliber Colt New Line before turning into a S&W Model 1 in the next shot.
Colt Walker
The preceding judge at McCall's trial (for Hickok's murder), Magistrate Claggett (Marshall Bell), uses a Colt Walker as a makeshift gavel in "The Trial of Jack McCall" (S1E05).
Remington 1875
Seth Bullock (Timothy Olyphant) carries a Remington 1875 throughout the series, including his term as sheriff of Deadwood. Dan Dority (W. Earl Brown) also occasionally carries a Remington 1875.
Lefaucheux pinfire pocket revolver
In the pilot episode "Deadwood" (S1E01), the so-called "derringer" that Trixie (Paula Malcomson) uses to shoot and kill one of her customers at the Gem Saloon actually appears to be a Lefaucheux pinfire pocket revolver, which Al Swearengen (Ian McShane) takes from her. This was based on a real-life incident in Deadwood in which a prostitute shot one of her clients through the head and he survived for twenty minutes, muttering.
Remington 1866 Derringer
Trixie (Paula Malcomson) receives another gun, a Remington 1866 Derringer, from Jewel "the gimp" (Geri Jewell) but gives it to Swearengen at the end of the pilot episode. (However, a continuity error switches this gun to both an NAA Mini-Revolver and a Smith & Wesson Model 1 at the beginning of the next episode). Cy Tolliver (Powers Boothe) uses a derringer to kill Miles Anderson (Greg Cipes) in Suffer the Little Children (1.08), but this too becomes a S&W Model 1 when he hands it to Joanie Stubbs (Kim Dickens), who later conceals a black-gripped derringer in New Money (2.03). In Something Very Expensive (2.06), Maddie (Alice Krige) unsuccessfully threatens Francis Wolcott (Garret Dillahunt) before he takes it from her.
Smith & Wesson Schofield
In the pilot episode "Deadwood" (S1E01), Al Swearengen (Ian McShane) keeps a Smith & Wesson Schofield on his nightstand which he pulls under the sheets when Trixie enters his room.
Smith & Wesson Model 1 1/2
In a three-part continuity error, Trixie's Remington Derringer/Colt New Line is now a Smith & Wesson Model 1 1/2 in a shot in "Deep Water" (S1E02). Cy Tolliver (Powers Boothe) hands Joanie Stubbs (Kim Dickens) a Model 1 1/2 to murder Flora Anderson (Kristen Bell) for attempting to steal from the Bella Union in "Suffer the Little Children" (S1E08). The pistol originally used by Cy to kill Flora's brother Miles was a Remington Derringer, but it is possible (although not likely) that he pocketed the derringer and gave Joanie a S&W Model 1 1/2 to shoot Flora.