About 38 Special
Despite its name, its caliber is actually 0.357 inches. Except for its length, the .38 Special case is identical to that of the .357 Magnum which was developed from the earlier cartridge in 1935. This allows the .38 Special round to be used in revolvers chambered for the .357 Magnum (but not the reverse).
The .38 Special was introduced in 1902 as a development of the .38 Long Colt cartridge which, as a military service cartridge, was found to have inadequate stopping power during the Philippines Insurrection. It was originally loaded with black powder but as smokeless gunpowders became popular in the early 20th century, the .38 special was adapted to the new propellants. The .38 Special is one of the most successful handgun cartridges. More than a century after its introduction, it remains popular for self-defense, hunting small game, and target shooting.
In the 1930s, heavy framed revolvers oriented toward target shooting, such as the S&W "38/44 Heavy Duty", allowed development of a higher pressure (and therefore higher power) version called the .38 Special Hi-Speed and, eventually, the .357 Magnum. These .38 revolvers, built on a larger frame originally designed for the .44 Special, survived for about three decades before the .357 revolvers outdid them in sales. Today, versions of this cartridge loaded to slightly higher pressure are available, called .38 Special +P; these are usable in .38 revolvers rated +P and in .357 Magnum revolvers.