Former Confederate soldier Cullen Bohannon (Anson Mount) carries a Confederate-made Griswold & Gunnison Revolver in "Pilot" (S1E01), by which he is recognized. This weapon is only mainly seen in the pilot episode, after which Cullen Bohannon carries a Colt 1860 Army revolver as his main sidearm for the rest of the season. The Griswold & Gunnison revolver is also seen firing during a continuity error in "A New Birth of Freedom" (S1E03).
Colt 1860 Army
Cullen Bohannon (Anson Mount) carries a Colt 1860 Army revolver as his sidearm after the pilot.The 1860 was the most common handgun in the United States at the time, most had a brass trigger guard (see photo), they were not manufactured with a brass frame like the Griswold above. Several other characters carry and use the Colt 1860 Army revolver throughout the season, including Elam Ferguson (Common).
The brass framed pistol Bohannon uses in the opening episode is neither an 1860 nor a Griswold but is an amalgam reproduction that was likely used as a stop gap piece for filming.
Remington 1858 New Model Army
Former Union soldier Daniel Johnson (Ted Levine) carries a Remington 1858 New Army in "Pilot" (S1E01). Bolan (Ian Tracey), and other characters also carry Remington 1858 New Armys as their sidearms during the season. Most of the Remingtons appear to be modern and unauthentic replicas, known as "Texas Models", because brass-framed Remingtons were never manufactured.
Pepperbox pistol
A Pepperbox pistol is used by Thomas Durant in the series.
Colt 1872 Open Top
A Colt 1872 Open Top is the main sidearm used by the freedman Elam Ferguson.
Ethan Allen Double barreled pistol
An Ethan Allen pistol is used by Durant and Lily Bell in the series.
Rifles
Winchester 1866 "Yellowboy"
The Winchester 1866 "Yellow Boy" rifle is prevalent in many episodes, especially in "Timshel" (S1E09). The rifle, while period correct, would not have been issued to the US Cavalry as portrayed in the series. It is used by many characters throughout the series.
Shotguns
Double Barreled Percussion Shotgun
What appears to be a sawed-off Double Barreled Cartridge Shotgun and is seen pulled by Thor "The Swede" Gundersen (Christopher Heyerdahl) in (S1E02).