.357 Magnum

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 1,000 feet per second (300 m/s). 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 0.357 inches (9.07 mm) 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 .3801–.3809-inch-diameter (9.65–9.67 mm) 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 ¹⁄₈ inch (3.2 mm), 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 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 ¹⁄₈ 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 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 to withstand.

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.

Performance

This cartridge is regarded by many as an excellent self-defense round. For big game, such as bears and large ungulates, which have a substantially sturdier build than humans, it is inferior to the .500 Smith & Wesson, .50 Action Express, .44 Magnum, .454 Casull, .41 Magnum and other larger magnum rounds. Still, it is a fine small- and medium-game round and will kill deer very reliably at reasonable ranges if the right loads (140 grains (9.1 g) and heavier hollow-point bullets, and solid semiwadcutter bullets) are carefully used by a competent marksman. For further comparison, the .357 Magnum has a higher velocity at 100 yards (91 m) than its parent .38 Special has at the muzzle. Its stopping power on game is similar to that of the .45 Colt, and it has a flatter trajectory. It is a very versatile cartridge, and can be used with success for self-defense, plinking, hunting, or target shooting.

Revolvers in .357 Magnum caliber have the significant advantage of also being able to fire .38 Special ammunition, with its lower cost, recoil, noise, and muzzle flash. This trait makes .357 revolvers ideal for novice shooters who are not yet used to firing full-strength .357 loads but do not want the expense of buying a second lower-powered gun to train with. However, .38 Special ammunition should not generally be used with any .357 semiautomatic handgun or rifle, since such firearms require the larger recoil produced by firing a .357 Magnum round to cycle properly.

It has also become popular as a "dual-use" cartridge in short, light rifles like the American Old West lever-actions. In a rifle, the bullet will exit the barrel at about 1,800 feet per second (550 m/s), making it far more versatile than the .30 Carbine or the .32-20 Winchester. In the 1930s, it was found to be very effective against steel car doors and ballistic vests, 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 semi-automatic 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 9mm Winchester Magnum, which is also known as the 9×29mm, was developed to duplicate the performance of the .357 Magnum in a semi-automatic pistol.

Some common performance parameters are shown in the table below for several .357 Magnum loads. Bullet weights ranging from 110 to 180 grains (7.1 to 11.7 g) are common. The 125 grains (8.1 g) JHP loads are popular for self-defense, whereas the heavier loads are usually used for hunting. Loads are available with energies from about 400 to 700 foot-pounds force (540 to 950 J), and penetration depths from 9 to 27 inches (230 to 690 mm) are available for various applications and risk assessments.

Key: Expansion – expanded bullet diameter (ballistic gelatin). Penetration – penetration depth (ballistic gelatin). PC – permanent cavity volume (ballistic gelatin, FBI method). TSC – temporary stretch cavity volume (ballistic gelatin).

Comparison

The .357 Magnum was a direct competitor with the .38 Super.

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 shoot .38 Special wadcutter ammunition with good results. 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 yards' (18 m) 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.

The .357 Magnum was developed from the earlier .38 Special. This was possible because the .38 Special 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 bullet case. The 9×19mm Parabellum was introduced the same year (1902) but was originally designed for smokeless powder, and for higher pressures (~39,200 psi (270 MPa)). It therefore produces considerably more energy than the .38, despite its case having less than half the powder capacity. Many .38 Special loads use the same powders, in similar charge weights, but because the case is so much larger, 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 Magnum, together with the stronger revolvers designed to handle it, were developed.

The .357 SIG that was developed in 1994 was named "357" to highlight its purpose: to duplicate the performance of 125-grain (8.1 g) .357 Magnum loads fired from 4-inch-barreled (100 mm) revolvers, in a cartridge designed to be used in a semi-automatic pistol. Performance is similar to the 9×23mm Winchester. The .357 SIG provided a self-defense cartridge close in performance to a 125 gr .357 Magnum, but from a semi-automatic pistol with greater ammunition capacity.

Synonyms