.357 Magnum

The .357 Magnum has 1.66 milliliter (26.2 grain H
₂O) cartridge case capacity.

.357 Magnum maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm)^[10]

The cartridge headspaces on the rim of the case. The common rifling twist rate for this cartridge is 476 mm (1 in 18.74 in), six grooves, ø lands = 8.79 mm, ø grooves = 9.02 mm, land width = 2.69 mm, and the primer type is small pistol magnum.^[10]

According to the C.I.P. rulings, the .357 Magnum cartridge case can handle up to 300 MPa (44,000 psi) P_max piezo pressure. In C.I.P.-regulated countries, every pistol cartridge combination has to be proofed at 130% of this maximum C.I.P. pressure to certify for sale to consumers. This means that .357 Magnum-chambered arms in C.I.P.-regulated countries are currently proof-tested at 390 MPa (57,000 psi) PE piezo pressure.^[10]

This cartridge is regarded by many as an excellent hunting, metallic silhouette, and self-defense round.^{[citation needed]} With proper loadings, it can also be effective against large or dangerous game, such as bear and ungulates.^{[citation needed]} The .357 Magnum has less energy than the larger magnum revolver loadings, but is smaller in diameter, with high velocity, allowing for excellent penetration properties. It is a fine small- and medium-game round and is sufficient to hunt deer at reasonable ranges if a competent shooter uses suitable loadings. For further comparison, the .357 Magnum has a higher velocity at 100 yards (91 m) than its parent case (.38 Special) has at the muzzle.^[11] The .357 Magnum's effectiveness on game is similar to that of the .45 Colt, but with a much flatter trajectory due to its higher velocity. It has been used with success for self-defense, plinking, hunting, or target shooting.^{[12][better source needed]}

The original .357 Magnum load was a 158 gr (10.2 g) bullet with an advertised muzzle velocity of 1,525 ft/s (465 m/s) and muzzle energy of 816 ft⋅lbf (1,106 J). (Muzzle velocity was taken using a large frame revolver with a fairly long barrel of 8.75 in (222 mm)) Most of today's SAAMI- conforming loads are fairly mild compared to the original mid-1930s load. Today's C.I.P.-compliant loads can duplicate the original mid-1930s load. When using a revolver with a shorter 7 in (178 mm) barrel, today's C.I.P. conform maximum loads with a 158 gr (10.2 g) bullet can reach a muzzle velocity of 1,502 ft/s (458 m/s).^[13]

For a handgun cartridge, the bolt thrust is considerable at C.I.P. conform maximum loads and is an important factor in weapons design. The greater the bolt thrust, the stronger the locking mechanism has to be to withstand it. Revolvers chambered in .357 Magnum have the significant advantage of also being able to chamber and fire the shorter and less-powerful .38 Special cartridge. Compared to the .357 Magnum, .38 Special is also lower in cost, recoil, noise, and muzzle flash. The ability to also fire .38 Special also makes .357 revolvers ideal for novice shooters who are not yet used to firing full-power .357 Magnum 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 magnum semiautomatic handgun or rifle, since such firearms require the larger recoil produced by firing a .357 Magnum round to cycle properly.

The .357 Magnum 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),^[14] making it far more versatile than the .30 Carbine or the .32-20 Winchester.^{[dubious – discuss]} 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, state police, sheriffs and other police agencies. The .357 Magnum revolver has been largely replaced by modern, high-capacity semi-automatic pistols for police use. However, it is still very popular as a backup gun and among outdoorspeople, security guards, and civilians for hunting, metallic silhouette, target shooting, and self-defense. 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,^[15] as was the .357 SIG cartridge.

Some common performance parameters are shown in the table below for several .357 Magnum loads. Bullet weights ranging from 100 to 200 grains (6.5 to 13.0 g) are common. The 125 grains (8.1 g) jacketed hollow-point loads are popular for self-defense, whereas heavier loads are commonly used for hunting.^{[citation needed]} Loads are available with energies typically from 400 to 800 foot-pounds force (542 to 1,085 joules) and can be selected for various applications based on desired use 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)

The .357 Magnum cartridge has accuracy potential comparable to that of the .38 Special wadcutter round, which is often regarded as a benchmark for precision shooting. Revolvers chambered for .357 Magnum can also fire .38 Special wadcutter ammunition with good accuracy. This combination of precision, power, and the ability to use less-expensive, lower-recoil .38 Special cartridges contributes to the versatility of .357 Magnum revolvers. As a result, they are used in a range of shooting activities, from short-range precision shooting at approximately 20 yards (18 m) to longer-range falling-plate competitions. The cartridge is also commonly chosen by individuals who handload ammunition, as it is relatively economical to reload and is known for consistent performance.^[17]

The .357 Magnum was developed from the earlier .38 Special. This was possible because the .38 Special was introduced in 1898 and originally designed to use black powder, which requires two to five times as much powder by volume to produce the same velocity with the same bullet as smokeless powder. Thus, the .38 Special has a relatively large case capacity, and for lower pressures (121 MPa (17,500 psi) P_max piezo pressure). The 9×19mm Parabellum was introduced in 1902 and was originally designed to use smokeless powder, and for higher pressures (235 MPa (34,100 psi) P_max piezo pressure).^[18] 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 at similar charge weights, but because the case is so much larger, light-target loads with fast-burning powders may only fill the case about 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, was developed.

The .357 SIG, developed in 1994, was named "357" to highlight its intended purpose: to duplicate the performance of 125-grain (8.1 g) .357 Magnum loads fired from 4-inch-barreled (102 mm) revolvers, in a cartridge designed to be used in a semi-automatic pistol.^{[citation needed]}

• 
  Colt Pythons in 8" and 6" barrels
• 
  Smith & Wesson Model 686
• 
  Ruger GP100 (mod. KGP-161)

• .357 AMP
• .357 Remington Maximum
• .357 SuperMag
• .327 Federal Magnum
• 9×25mm Mauser
• 9×29mm, 9×30mm Grom – similar rimless cartridges
• Coonan Arms
• Table of handgun and rifle cartridges