|Place of origin||United States|
|Designer||Winchester Repeating Arms Company|
|Case type||Rimmed, bottleneck|
|Bullet diameter||.427 in (10.8 mm)|
|Neck diameter||.443 in (11.3 mm)|
|Shoulder diameter||.458 in (11.6 mm)|
|Base diameter||.471 in (12.0 mm)|
|Rim diameter||.525 in (13.3 mm)|
|Rim thickness||.065 in (1.7 mm)|
|Case length||1.305 in (33.1 mm)|
|Overall length||1.592 in (40.4 mm)|
|Case capacity||40 gr H2O (2.6 cm3)|
|Primer type||Large pistol|
|Maximum pressure||22,000 psi (150 MPa)|
|Test barrel length: 20"|
The .44-40 Winchester, also known as .44 Winchester, .44 WCF (Winchester Center Fire), and .44 Largo (in Spanish-speaking countries) was introduced in 1873 by the Winchester Repeating Arms Company. It was the first metallic centerfire cartridge manufactured by Winchester, and was promoted as the standard chambering for the new Winchester Model 1873 rifle. As both a rifle and a handgun caliber, the cartridge soon became widely popular, so much so that the Winchester Model 1873 rifle became known as "The gun that won the West."
When Winchester released the new cartridge, many other firearm companies chambered their guns in the new round. Remington and Marlin released their own rifles and pistols which chambered the round, Colt offered an alternative chambering in its popular Single Action Army revolver in a model known as the Colt Frontier Six-Shooter, and Smith & Wesson began releasing their Smith & Wesson New Model 3 chambered in .44-40. Settlers, lawmen, and cowboys appreciated the convenience of being able to carry a single caliber of ammunition which they could fire in both pistol and rifle. In both law enforcement and hunting usage, the .44-40 became the most popular cartridge in the United States, and to this day has the reputation of killing more deer than any other save the .30-30 Winchester.
The cartridge was originally sold as .44 Winchester. When the Union Metallic Cartridge Co. (UMC) began selling their own version of the cartridge, it adopted the name .44-40 (shorthand for .44 caliber and the standard load at the time of 40-grain (2.6 g) of black powder), as it did not want to offer free advertising for one of its competitors. Over time, the name stuck, and eventually Winchester adopted the .44-40 designation for the round after World War II. Winchester uses the designation "44-40 Winchester" on packaging.
The initial standard load for the cartridge was 40 grains (2.6 g) of black powder propelling a 200-grain (13 g) round-nose, flat-point bullet at roughly 1,245 ft/s (379 m/s). Winchester catalogues listed velocities of 1,300 ft/s (400 m/s) by 1875. In 1886, UMC also began offering a slightly heavier, 217-grain (14.1 g), bullet at 1,190 ft/s (360 m/s), also with 40 gr of black powder. Winchester soon began to carry the 217-gr loading, as well, but in 1905, UMC discontinued the heavier load. In 1895, Winchester introduced a 200-grain (13 g) cartridge bulk loaded with 17-grain (1.1 g) of DuPont No. 2 smokeless powder and a bullet for 1,300 ft/s (400 m/s), and in 1896, UMC followed suit with a 217-gr bullet at 1,235 ft/s (376 m/s). Soon, both companies were offering the cartridge with lead "metal patched" (i.e. copper-jacketed with lead points), and full metal jacket versions. Taking advantage of the stronger-action designs of the Winchester model 1892 and the Marlin 1894 lever-action rifles, in 1903, Winchester began offering a higher-performance version of the loading called the Winchester High Velocity (WHV), with a velocity of 1,540 ft/s (470 m/s) using a 200-gr copper-jacketed bullet from a 24-inch (610 mm) barrel length, UMC and Peters Cartridge Company soon introduced equivalents. Over the years, a number of different bullet weights and styles have been offered, including 122, 140, 160, 165, 166, 180, and 217 gr in lead, soft- and hollow-point, full metal case, blanks, and shot shells. The most common current loading is a 200-gr bullet at 1190 ft/s.
By 1942, more modern cartridges had all but eclipsed the .44-40, but it regained some popularity in the 1950s and 1960s when Colt began once again to manufacture the Single Action Army and Frontier. More recently, the .44-40 has had a resurgence due to the popularity of metallic silhouette and cowboy action shooting, which inspired the introduction of a low-velocity 225-grain (14.6 g) gallery load, the heaviest factory bullet ever available for the cartridge.