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The .357 S&W Magnum (9×33mmR), or simply .357 Magnum, is a revolver cartridge with a .357-inch (9.07 mm) bullet diameter, created by Elmer Keith, Phillip B. Sharpe, and Colonel D. B. Wesson〔 of firearms manufacturer Smith & Wesson, and Winchester. It is based upon Smith & Wesson's earlier .38 Special cartridge. The .357 Magnum cartridge was introduced in 1934, and its use has since become widespread. This cartridge started the "Magnum" era of handgun ammunition. The .357 Magnum cartridge has a positive reputation for stopping power. ==Design== The .357 Magnum was collaboratively developed over a period in the early to mid-1930s by a group of individuals in a direct response to Colt's .38 Super Automatic. At the time, the .38 Super was the only American pistol cartridge capable of defeating automobile cover and the early ballistic vests that were just beginning to emerge in the post-World War I "Gangster Era."〔 Tests at the time revealed that those vests defeated any handgun cartridge traveling at less than about . 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. Though .38 and .357 would seem to be different diameter chamberings, they are in fact identical, as is the true bullet diameter of the .38 Special cartridge. The .38 Special nomenclature relates to the previous use of heeled bullets (such as the .38 Short Colt), which were the same diameter as the case. Thus, the only external difference in the two cartridges is a slight difference in length, solely for safety purposes. Much credit for the .357's early development is given to hunter and experimenter Elmer Keith. Keith's early 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. The .38-44 HV load used the .38-Special cartridge loaded to a much higher velocity than standard .38-Special ammunition. The .38-44 revolvers were made by using a .44 Special size gun with the barrel bored to accept .357-caliber bullets (the true bullet diameter of the .38 Special) and the cylinder bored to accept cartridges (where the name “38 Special” originated). Since the frame, cylinder, and barrel were much stronger than the standard .38 Special components, it was capable of withstanding much higher pressures. The .38-44 HV round, while no longer available, was in most cases the equal of the later .357 Magnum, which works at more than double the pressure of standard .38 Special. The .357 Magnum addresses the safety issues which earlier cartridges had by lengthening the case by approximately , preventing the high-pressure .357 cartridge from chambering (fitting) in a firearm designed for the shorter, lower-pressure .38 Special. Elmer Keith also contributed the Keith-style bullet, which increased the mass of bullet located outside the cartridge, while leaving more room inside the cartridge for powder. The Keith bullet also employed a large, flat meplat, thus enabling rapid energy transfer for greater wounding properties. At the same time, this bullet design does not deform like a hollow point, and as a result achieves greater penetration. These characteristics of the Keith bullet make it very suitable for hunting applications as well as for target shooting. In order to reassert itself as the leading law-enforcement armament provider, Smith & Wesson developed the .357 Magnum, with Colonel D. B. Wesson leading the effort within Smith & Wesson, along with considerable technical assistance from Phillip B. Sharpe, a member of the Technical Division staff of the National Rifle Association. The new round was developed from Smith & Wesson's existing .38 Special round. It used a different powder load, and ultimately the case was extended by . The case extension was more a matter of safety than of necessity. Because the .38 Special and the early experimental .357 Magnum cartridges loaded by Keith were identical in physical attributes, it was possible to load an experimental .357 Magnum cartridge into a .38 Special revolver, with potentially disastrous results. Smith & Wesson's solution, of extending the case slightly, made it impossible to chamber the magnum-power round in a gun not designed for the additional pressure.〔 However, both .38 Special and .357 Magnum will chamber in Colt New Army revolvers in .38 Long Colt, due to the straight-walled chambers, but this should not be done under any circumstances, due to dangerous pressure levels, up to three times what the New Army is designed for. The choice of bullet for the .357 Magnum cartridge varied during its development. During the development at Smith & Wesson, the original Keith bullet was modified slightly, to the form of the Sharpe bullet, which itself was based upon the Keith bullet, but which had 5/6 of the bearing surface of the Keith bullet, Keith bullets typically being made oversized and sized down. Winchester, however, upon experimenting further during the cartridge development, modified the Sharpe-bullet shape slightly, while keeping the Sharpe contour of the bullet. The final choice of bullet was hence based upon the earlier Keith and Sharpe bullets, while additionally having slight differences from both. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「357 magnum」の詳細全文を読む スポンサード リンク
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