The .36 caliber pistol, Colt’s or otherwise, was an almost ideal size handgun for weight, balance, and accuracy.
As for the popular .36 caliber round ball, at a weight of 80 grains, backed by a 22- to 25-grain charge of black powder, an 1851 Navy had a muzzle velocity in the neighborhood of 850 fps; delivering sufficient mass and velocity for a fight ending shot at typical gunfight distances, which could have been anything from arms length to 50 feet or more.
Further, the “or more” was proven in 1865 by Wild Bill Hickok, who famously and very publicly extended the effective accuracy of the 1851 Navy in a gunfight to a distance of some 225 feet.
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In the late Civil War era, Colt’s, Remington, and other arms makers built a greater number of .36 caliber handguns, including Pocket Pistols. The Colt 1861 Navy (same caliber as the 1851 Navy but styled like the 1860 Army), was the basis for the scaled down 1862 Police Model designed by Sam Colt in 1861.
The Civil War .36 caliber percussion models, even converted to .38 caliber metallic cartridge pistols (first to .38 Colt rimfire and later .38 Colt centerfire cartridges), remained so popular, that Colt’s continued to manufacture the Pocket Models until the early 1880s, making the .36 caliber Colts and their variations, some of the most famous of all Guns of the Gunfighters.
As for the popular .36 caliber round ball, at a weight of 80 grains, backed by a 22- to 25-grain charge of black powder, an 1851 Navy had a muzzle velocity in the neighborhood of 850 fps; delivering sufficient mass and velocity for a fight ending shot at typical gunfight distances, which could have been anything from arms length to 50 feet or more.
Further, the “or more” was proven in 1865 by Wild Bill Hickok, who famously and very publicly extended the effective accuracy of the 1851 Navy in a gunfight to a distance of some 225 feet.

The .36 Caliber Pistol – A Popular Choice With Early Gunfighters
Sam Colt may have created the 1851 Navy, but Wild Bill Hickok made the .36 caliber Colt pistols immortal. Indeed,

In the late Civil War era, Colt’s, Remington, and other arms makers built a greater number of .36 caliber handguns, including Pocket Pistols. The Colt 1861 Navy (same caliber as the 1851 Navy but styled like the 1860 Army), was the basis for the scaled down 1862 Police Model designed by Sam Colt in 1861.
The Civil War .36 caliber percussion models, even converted to .38 caliber metallic cartridge pistols (first to .38 Colt rimfire and later .38 Colt centerfire cartridges), remained so popular, that Colt’s continued to manufacture the Pocket Models until the early 1880s, making the .36 caliber Colts and their variations, some of the most famous of all Guns of the Gunfighters.