Marshall Reuben J. "Rooster" Cogburn (John Wayne) keeps a Colt Single Action Army or "Peacemaker" with a 4 3/4" barrel, known as the "Quick Draw" model as his sidearm of choice throughout the film. "Lucky" Ned Pepper (Robert Duvall) also keeps a Quick Draw Peacemaker which he uses when facing Rooster during the film's climax. While watching Rooster load his Peacemaker, Mattie Ross (Kim Darby) asks him why he keeps one chamber empty, to which he replies, "So I won't shoot my foot off." At one point in the film, Rooster tells Mattie about how when he was in the Civil War, he did the same dual wielding guns method while on horseback, which he claims he fired two "Navy '60s" with the reins in his mouth, despite the fact that the Colt 1860 was the Army revolver, not the Navy. The 1851 and 1861 models were the Navy guns.
Rooster Cogburn (John Wayne) keeps a Winchester 1892 "Saddle Ring Carbine" with a large lever loop chambered in .44-40 as his rifle of choice throughout the film and is most notabley seen using it during the film's climax when he fires it akimbo style along with his Single Action Army, twirling the rifle with the large lever loop to cock it with one hand. (This action most likely inspired the same technique used by Arnold Schwarzenegger with the Winchester Model 1887 shotgun in T2).
Mattie Ross (Kim Darby) inherits her father's civil war handgun when he dies, which is a Colt Walker 1847 revolver with a cartridge conversion (although it is said to be a percussion gun to stay true to the novel). Mattie uses it when she encounters Tom Cheney (Jeff Corey) and is knocked down by the recoil of the gun (which is a bit unrealistic) and manages to shoot him in the gut with it. He then manages to charge her and take the gun do to several misfires (which were at fault of Rooster because he a had previously loaded it wrong while drunk, and also overloaded the chambers with powder which cause such great recoil.) The gun manages to fire once more in the hands of Mattie and manages to graze Cheney's head though the recoil knocks her into a snake pit. When Mattie first shows the gun to Rooster, he calls it a Colt's Dragoon but it is clearly too large and lacks a loading lever latch like all of the Dragoon models had.
La Boeuf (Glen Campbell) uses a Sharps 1874 Cavalary Carbine as his rifle of choice throughout the film. When hunting, he manages to pretty much destroy a Turkey with the rifle. Later in the film he manages to shoot Ned Pepper's horse from a long distance and is mocked by Rooster for missing the shot claiming, "Maybe next time if you aim for for the horse, you might hit Pepper." He fairs better at the film's climax and manages to shoot Pepper off his horse from an impressive distance before he kills Rooster.
Lucky Ned Pepper (Robert Duvall) is seen in a few scenes using a Colt New Service revolver mocked up to look like a Single Action Army by adding a fake ejector rod. (See also The Long Riders.) These guns were used by actors too slow to handle a single action only revolver and required a double action trigger pull for quicker shots. It is strange why he uses this gun as he is never required to fire it rapidly and when facing Rooster at the end of the film, the gun switches to an actually SAA instead.
Winchester 1866 "Yellow Boy" (mocked up like Henry 1860)
Tom Cheney (Jeff Corey) is seen using a Winchester 1866 "Yellow Boy" rifle with the forend removed to look like a Henry 1860 rifle to murder Frank Ross (John Pickard), Matties' father. Dialogue confirms they intended the gun to be a Henry rifle in the film. Later, Cheney is seen with an actually Henry instead.
A U.S. Marshal helping Rooster Cogburn unload the outlaws from the Indian territory is armed with a 12 Gauge Double Barreled Shotgun. Later, Farrell Parmalee (Kenneth Becker) is seen armed with a side-by-side as well.
A U.S. Marshal helping unload outlaws from the Indian territory is seen armed with a Winchester 1894 Saddlering Carbine rifle. He is seen with it inhand when telling Mattie to wait another day to talk to Rooster Cogburn. Later in the film, Ned Pepper is seen with a '94 rifle and fires it into the air to let Rooster know where he is. It clearly has a longer reciever and the more complex lever system under the gun helping tell it from an 1892 rifle.
