A stainless steel Ruger Blackhawk revolver is used by John Dutton (Kevin Costner) at the beginning of the series premiere "Daybreak" (S1E01).
Pistols
Kimber Custom II
The standard service weapon for all Montana Livestock Agents in the show appear to be Kimber Custom TLE II pistols.
Glock 17
A Glock 17 pistol is seen used throughout the series. It is first seen taken from and used by Kayce Dutton (Luke Grimes) in the series premiere "Daybreak" (S1E01).
Glock 19
When Kayce is out training, he is seen using a Glock 19 during a transition drill in "No Good Horses" (S1E03). Later on in the same episode, Kayce uses the Glock 19 to kill one serial killer and wound another.
Unknown 1911
An unknown M1911 variant pistol is seen used by John Dutton's longtime Ranch Hand Lloyd Pierce (Forrie J. Smith) when disposing of a ex-Yellowstone Ranch Hand for attacking Jimmy.
Rifles/Carbines
Marlin Model 336
The Marlin Model 336 is a rifle seen used throughout the series.
M1 Carbine
An M1 Carbine is seen carried by a Native American guarding cattle in the series premiere "Daybreak" (S1E01).
Custom AR-15
A custom AR is used by Lee Dutton (Dave Annable), John's oldest son, in "Daybreak" (S1E01) when confronting Kayce's brother-in law.
Custom AR Pistol
While training, Kayce Dutton (Luke Grimes) is seen practicing with his own personal custom AR Pistol fitted with a Trijicon MRO red dot sight, flash suppressor, SB Tactical SBPDW Brace, Free Floating MLOK Rail, and Magpul PMag.
Daniel Defense MK18 Pistol
Several tribesmen are armed with what appear to be Daniel Defense MK18 AR Pistols with SB Tactical SOB pistol braces.
Winchester Model 1894
A Winchester Model 1894 is used by a Dutton rancher in the series premiere "Daybreak" (S1E01). Later in the season, John Dutton (Kevin Costner) uses a Winchester Model 1894 when dealing with unruly Chinese tourists who stubbornly trespass on his property as well as being dangerously close to a bear.
M16A2
M16A2 rifles are seen used by Tribal Police Officers during the standoff with Dutton Ranchers in the series premiere "Daybreak" (S1E01).
Shotgun
Remington 870
Sam Stands Alone (Tokala Black Elk) uses a Remington 870.