The .38 Smith & Wesson Special (commonly .38 Special, .38 Spl, or .38 Spc, pronounced “thirty-eight special”) is a rimmed, center fire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although some semi-automatic pistols and carbines also use this round. The .38 Special was the standard service cartridge of most police departments in the United States from the 1920s to the early 1990s, and was also a common sidearm cartridge used by soldiers in World War I. In other parts of the world, it is known by its metric designation of 9×29.5mmR or 9.1x29mmR.
Notes by Jim Waddell; Movies & TV call it 38 caliber! Wrong! Despite its name, the .38 Special caliber is actually .357–.358 inches (9.0678 mm), with the “.38″ referring to the approximate diameter of the loaded brass case. This came about because the original .38-caliber cartridge, the .38 Short Colt, was designed for use in converted .36-caliber cap-and-ball (muzzle-loading) Navy revolvers, which had cylindrical firing chambers of approximately 0.374-inch (9.5 mm) diameter, requiring heeled bullets, the exposed portion of which was the same diameter as the cartridge case (see the section on the .38 Long Colt). Except for case length, the .38 Special is identical to that of the .38 Long Colt, and the .357 Magnum. This allows the .38 Special round to be safely fired in revolvers chambered for the .357 Magnum, and the .38 Long Colt to be fired in revolvers chambered for .38 Special, increasing the versatility of this cartridge. However, the longer and more powerful .357 Magnum cartridge will not chamber and fire in weapons rated specifically for 38 Special (e.g. all versions of the Smith & Wesson Model 10), which are not designed for the greatly increased pressure of the magnum rounds. The .38 Special was introduced in 1898 as an improvement over the .38 Long Colt which, as a military service cartridge, was found to have inadequate stopping power against the wooden shields of charging Moros during the Philippine-American War. Upon its introduction, the .38 Special was originally loaded with black powder, but the cartridge’s popularity caused manufacturers to offer smokeless powder loadings within a year of its introduction. During the late 1920s, a new standard-charge loading for the .38 Special was developed by Western Cartridge Company using a 200-grain (13g) round-nosed lead ‘Lubaloy’ bullet, the .38 Super Police. Remington-Peters also introduced a similar loading. Testing revealed that the longer, heavier 200-grain .38-calibre bullet fired at low velocity tended to ‘keyhole’ or tumble upon impact, providing more shock effect against unprotected personnel. At the same time, authorities in Great Britain were also testing the same 200-grain bullet in the smaller .38 S&W cartridge, which became known as the .38 S&W Super Police or the .38/200. Britain would later adopt the .38/200 as its standard military handgun cartridge. In 1930, Smith & Wesson introduced a large frame .38 Special revolver with a 5-inch (125mm) barrel and fixed sights intended for police use, the Smith & Wesson .38/44 Heavy Duty. The following year, a new high-power loading called the .38 Special Hi-Speed with a 158-grain metal-tip bullet was developed for these revolvers in response to requests from law enforcement agencies for a handgun bullet that could penetrate auto bodies and body armor. That same year, Colt Firearms announced that their Colt Official Police would also handle ‘high-speed’ .38 Special loadings. The .38/44 high-speed cartridge came in three bullet weights: 158, 150, and 110-grain, with either coated lead or steel jacket, metal-piercing bullets. The media attention gathered by the .38/44 and its ammunition eventually led Smith & Wesson to develop a completely new cartridge with a longer case length in 1934 – the .357 Magnum. During World War II, some U.S. aircrew (primarily Navy and Marine Corps) were issued .38 Special S&W Victory revolvers as sidearms in the event of a forced landing. In May 1943, a new .38 Special cartridge with a 158-grain, full steel jacketed, copper flash-coated bullet meeting the requirements of the rules of land warfare was developed at Springfield Armory and adopted for the Smith & Wesson revolvers. The new military .38 Special loading propelled its 158-grain bullet at a standard 850 ft/s (260 m/s) from a 4-inch (100 mm) revolver barrel. During the war, many U.S. naval and marine aircrew were also issued red-tipped .38 Special tracer rounds using either a 120-grain or 158-grain bullet for emergency signaling purposes. In 1956, the U.S. Air Force adopted the Cartridge, Caliber .38, Ball M41, a military variant of the .38 Special cartridge designed to conform to the rules of land warfare. The original .38 M41 ball cartridge used a 130-grain full metal jacketed bullet, and was loaded to an average pressure of only 13,000 psi, giving a muzzle velocity of approximately 725 ft/s (221 m/s) from a 4-inch (100 mm) barrel. This ammunition was intended to prolong the life of S&W M12 and Colt Air-crewman revolvers equipped with aluminum cylinders and frames, which were prone to stress fractures when fired with standard .38 ammunition. By 1961, a slightly revised M41 .38 cartridge specification known as the Cartridge, Caliber .38 Ball, Special, M41 had been adopted for U.S. armed forces using .38 Special caliber handguns. The new M41 Special cartridge used a 130-grain FMJ bullet loaded to a maximum allowable pressure of 16,000 psi for a velocity of approximately 950 ft/s (290 m/s) in a solid 6-inch (150 mm) test barrel, and about 750 ft/s (230 m/s) from a 4-inch (100 mm) revolver barrel. The M41 ball cartridge was first used in .38 revolvers carried by USAF aircrew and Strategic Air Command security police, and by 1961 was in use by the U.S. Army for security police, dog handlers, and other personnel equipped with .38 Special caliber revolvers. A variant of the standard M41 cartridge with a semi-pointed, unjacketed lead bullet was later adopted for CONUS (Continental United States) police and security personnel. At the same time, .38 tracer cartridges were reintroduced by the US Navy, Marines, and Air Force to provide a means of emergency signaling by downed aircrew. Tracer cartridges in .38 Special caliber of different colors were issued, generally as part of a standard aircrew survival vest kit. A request for more powerful .38 Special ammunition for use by Air Police and security personnel resulted in the Caliber .38 Special, Ball, PGU-12/B High Velocity cartridge. Issued only by the U.S. Air Force, the PGU-12/B had a greatly increased maximum allowable pressure rating of 20,000 psi, sufficient to propel a 130-grain FMJ bullet at 1,125 ft/s (343 m/s) from a solid 6-inch (150 mm) test barrel, and about 950-980 ft/s from a 4-inch (100 mm) revolver barrel. The PGU-12/B High Velocity cartridge differs from M41 Special ammunition in two important respects – the PGU-12/B is a much higher-pressure cartridge, with a bullet deeply set and crimped into the cartridge case. During the 1970s, new high-pressure (18,500 CUP) loadings of the .38 Special were introduced, known as .38 Special +P. This ammunition is usable in .38 revolvers designed for such ammunition, as well as in .357 Magnum revolvers. Another high-velocity load made by manufacturers such as Federal and Winchester, is sometimes labeled “For Law Enforcement Only” and designated .38 Special +P+. This ammunition is meant to be only used in .38 Special revolvers specially proofed for this load and can cause significant damage to firearms rated for only .38 Special or .38 Special +P. As with other .38 Special rounds, the +P+ loadings can also be fired safely in .357 revolvers, since the pressure developed by .38 Special +P+ loadings are typically around 22,000 psi, while .357 Magnum loadings typically achieve up to 35,000 psi. Because the .38 Special cartridge can be fired in .357 Magnum firearms, the former is a popular option due to its reduced recoil, lower noise, and lower cost. Due to its black powder heritage, the .38 Special is a low pressure cartridge, one of the lowest in common use today at 17,000 PSI. By modern standards, the .38 Special fires a medium-sized bullet at rather low speeds. The closest comparisons are the .380 ACP, which fires much lighter bullets slightly faster than most .38 Special loads; the 9x19mm Parabellum, which fires a somewhat lighter bullet significantly faster; and the .38 Colt Super, which fires a comparable bullet significantly faster. All three of these are usually found in semi-automatic pistols. The higher-pressure .38 +P loads at 20,000 PSI offer about 20% more muzzle energy than standard-pressure loads and places between .380 ACP and 9 mm Parabellum, similar to that of 9x18mm Makarov.