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The .357 Magnum (9.1×33mR) is a revolver cartridge created by Elmer Keith, Phillip Sharpe and the firearms manufacturer Smith & Wesson, based upon Smith & Wesson's earlier .38 Special cartridge. The .357 Magnum cartridge was introduced in 1934, and its use has since become widespread.
The .357 Magnum was developed over a period of time in the early to mid-1930s in a direct response to Colt's .38 Super. At the time, the .38 Super was the only pistol cartridge capable of defeating automobile cover and the early bulletproof vests that were just beginning to emerge in the post-World War I "Gangster Era". Tests at the time revealed that those early vests defeated any handgun cartridge traveling at less than about 1000 fps. Colt's .38 Super Automatic just edged over that velocity and was able to penetrate car doors and vests that bootleggers and gangsters were employing as cover.
In order to reassert itself as the leading law enforcement armament provider, Smith & Wesson developed the .357 Magnum. The new round was developed from its existing .38 Special round; it used a different powder load, and ultimately the case was extended by 1/8th of an inch (3.2 mm). The case extension was more a matter of safety than of necessity. Because the .38 Special and the early experimental .357 Magnum cartridges were identical in physical attributes, it was possible to load an experimental .357 Magnum cartridge in a .38 Special revolver, with potentially disastrous results. Extending the case slightly made it impossible to chamber the magnum power round in a gun not designed for the additional pressure.
Much credit for the .357's development is given to hunter and experimenter Elmer Keith. Keith's work in loading the .38 Special to increasingly higher pressure levels was made possible by the availability of heavy, target shooting-oriented revolvers like the Smith & Wesson 38/44 "Heavy Duty" and "Outdoorsman", .38-caliber revolvers built on .44-caliber frames. While the .38 Special cartridge is limited to 16,500 c.u.p. (copper units of pressure), the .357 Magnum is loaded to 35,000 c.u.p. The objective was to create a handgun cartridge that combined deep penetration, flat trajectory, and long range.
This cartridge is an excellent self-defense round; it still enjoys a reputation of being the gold standard of stopping power among handgun cartridges. Some of those who have used it have described a "struck by lightning" reaction in those hit with it. For big game, such as ungulates and bears (which have a sturdier build than humans), it is inferior to the .44 Magnum, .454 Casull, .41 Magnum and other bigger magnum rounds. Still, it is a fine small and medium game round and will kill deer very reliably at short range if the right loads (140 grain and heavier hollowpoint bullets) are carefully used by a qualified marksman. It has much more stopping power on game than the .45 Long Colt and a much flatter trajectory, making it easier to take small game out to about 75 yards (69 m). It is a very versatile cartridge, and can be used with success for self defense, plinking, hunting, or target shooting. Guns in .357 Magnum caliber have the advantage of being able to fire .38 Special ammunition, with its lower cost, recoil, noise, muzzle flash, and, often, better accuracy. It has also become popular as a "dual use" cartridge in short, light rifles like the Old West lever-actions. In a rifle, the bullet will exit the barrel at about 1800 feet per second, making it far more versatile than the .30 Carbine or the .32-20 Winchester. In the 1930s, it was found to be very effective on steel body armour, and metal-penetrating rounds were once popular in the United States among highway patrol and other police organizations. The .357 revolver has been largely replaced by modern, high-capacity semiautomatic pistols for police use, but is still very popular for backup gun use, and among outdoorsmen, security guards, and civilians for self defense and hunting.
The .357 Magnum was a direct competitor with the .38 Super, which was designed for semi-automatic pistols. The .38 Super can still give the .357 Magnum serious competition in barrels of equal length, but the .357 Magnum is more powerful especially because revolvers can have a longer barrel that would be too clumsy for semi-auto designs.
In terms of accuracy, the .357 Magnum has at least the same potential for precision shooting as the benchmark .38 Special wadcutter round—indeed, a good .357 Magnum revolver will happily shoot .38 Special wadcutter ammunition and return good results. With tailored loads in a clean, sound revolver, wadcutter or semi-wadcutter target rounds (with a lead bullet and a smaller charge of fast burning powder) will return groups as small as 1.5 inches (3.8 cm) from center to center of the two most widely-spaced shots at a range of 25 yards (23 m) with very little noise or recoil. Full power loads with good jacketed bullets and a heavy charge of a much slower burning powder can aspire to 2-1/2 inch (6.35 cm) groups with no great difficulty, and a good revolver firing loads it likes can also be made to produce 1.5-inch 25-yard groups (6 minutes of angle). It is this accuracy and power, and the versatility of also being capable of using less-expensive, milder .38 Special ammunition, that makes a .357 Magnum revolver an excellent gun for many different disciplines, from 20 yard precision shooting to long range falling-plate events. It is an excellent round for those considering handloading ammunition, as it is economical and consistently performs well in all but the strangest of load configurations.
As mentioned above, the .357 Magnum was developed from the earlier .38 Special. This was possible because the .38 was originally designed to use black powder, which requires two to five times as much powder by weight to produce the same velocity with the same bullet as does the much more efficient smokeless powder. Thus the .38 Special has a relatively large case; the 9mm Parabellum was introduced the same year, 1902, but was originally designed for smokeless powder, and for higher pressures (~35,000 psi). It therefore produces considerably more power than the .38, despite its case having less than 1/2 the powder capacity. Most 9mm powder charges fill the case to the base of the bullet, and some are heavily compressed. Many .38 Special loads use the same powders, in similar charge weights, but because the case is so much larger those charges only fill the case about 1/2 full; light target loads with fast burning powders may only fill the case perhaps 1/8 full. Filling the case with slower-burning powders produces much more power, but also much more pressure—far too much pressure for older, smaller-frame revolvers chambered in .38 Special. It was to accommodate these high-pressure, high-power loads that the longer .357, together with the stronger revolvers designed to handle it, was developed.
- Winchester 125 gr (8.1 g) Jacketed HP = 1450 ft/s (440 m/s), 583 ft•lbf (790 J)
- Winchester 158 gr (10.2 g) Jacketed HP = 1235 ft/s (375 m/s), 535 ft•lbf (725 J)
- .357 mag
- .357 S&W Magnum
- .357 Mangle'em (slang)
- 9x33mmR (European Designation)
- .38 Special
- 9 mm Luger
- .44 Magnum
- .357 SIG
- Colt Python
- Desert Eagle
- S&W Model 27
- S&W Model 686
- List of handgun cartridges
- List of rifle cartridges
- Marlin 1894C carbine
- Coonan pistol - semi-automatic pistol in .357 Magnum