.40 S&W

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The .40 S&W is a 10 mm pistol rimless cartridge designed by Smith & Wesson, a famous American firearms manufacturer.

1 History
2 Performance
3 Case failure reports
- 3.1 External Balistics
4 Synonyms
5 See also
6 External links
7 References

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History

The .40 S&W cartridge evolved from the 10 mm Auto pistol ammunition which had been adopted by the FBI, but turned out to be too powerful. The 10 mm Auto gave performance akin to the .41 Magnum pistol round, and recoil and muzzle blast, especially in a short barrel were found to be just too much for many shooters. Essentially it was found that a pistol powerful enough for deer was just not needed for the purpose of defense or law enforcement. The FBI started using a lowered charge version of the 10 mm Auto ammunition, a subsonic load often referred to as the "FBI load" or "10 mm lite." Smith & Wesson redesigned the cartridge to make it shorter while maintaining the performance of the FBI load. The .40 S&W cartridge quickly surpassed the 10 mm cartridge in popularity and units sold. With the .40 S&W being shorter than the 10 mm Auto and approximately the same length as the 9 mm Luger cartridge, many existing 9 mm Luger pistols could be adapted by their respective manufacturers to fire the new cartridge.

The case of the original 10 mm Auto had the same head dimensions as the old .30 Remington that was designed in about 1906 for the Remington Model 8 semi-auto deer rifle. The bullet was the same diameter as the old .38-40 dual use rifle/revolver round from the Old West. The .38-40, long obsolete, was known for good stopping power, and the .40 S&W reflects this, in a far more compact package.

In a great irony, Austrian manufacturer GLOCK beat Smith & Wesson to the market with a pistol chambered in .40 S&W, the GLOCK 22 and 23. GLOCK's rapid introduction was aided by its engineering of a pistol chambered in 10 mm Auto only a short time earlier, the GLOCK 20. The GLOCK 20 was and still is considered an excellent pistol in 10 mm Auto, but has sold vastly fewer units than the .40 S&W GLOCKs.

Initial acceptance of the .40 S&W was slow, since the round was considerably less powerful than the 10 mm Auto it was based on. This lead to derogatory names such as ".40 Short and Wimpy" or ".40 Short and Weak." It was, however, a ballistically better choice than the 9 mm for police and defensive use, and it quickly gained popularity once pistol manufacturers began to adapt their 9 mm pistol designs to create additional models chambering .40 S&W.

The 40 S & W is dimensionally identical to the 10 mm Auto except for length. Both cartridges headspace on the mouth of the case. Thus in a semi-auto they are not interchangeable. Smith and Wesson does make a double action revolver that can fire either at will using moon clips. A single-action revolver in the 38-40 chambering can also be fitted out to fire the .40 or the 10 mm if it has an extra cylinder. The .40 will at short range take deer with loads that come close enough to the combination of .40 caliber or better, 200 grains (13 g) bullet or better, and 1000 feet per second or better, but is not designed for deer though of course is fine for small and medium game.

IMI attempted a similar cartridge in the 1980s, called the .41 Action Express (or .41 AE) for the Jericho 941 pistol. This cartridge was based on the .41 Magnum case, cut down to fit in a 9 mm frame, and using a rebated rim the same diameter as the 9 mm Luger. The .41 AE is ballistically similar to the .40 S&W, to the point that many reloading manuals suggest using .40 S&W load data in the .41 AE. The .41 AE is a more attractive cartridge in many ways, as the rebated rim allows a simple barrel and magazine change to allow most 9 mm guns to be converted to .41 AE. The .41 AE uses .410 inch bullets, whereas the .40 S&W uses .400 inch bullets. However, as it lacks the backing of ammunition manufacturers in making .410 caliber bullets suited to semiautomatic pistols, the .41 AE has not achieved widespread popularity.

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Performance

The new .40 S&W cartridge has become a huge success in the United States, because it is seen by many as much more capable than the 9 mm Luger, without the overkill of the 10 mm Auto cartridge. In the rest of the world it has become a popular combat pistol shooting sports cartridge.

In terms of muzzle velocity and energy, the .40 S&W exceeds all standard-pressure and +P 9 mm Luger loadings and many standard-pressure .45 ACP rounds, generating between 350 and 450 foot-pounds (475 and 610 joules) of energy, depending on bullet weight. .45 ACP +P rounds, however, generally exceed .40 S&W power levels.

The .40 S&W is considered by some the best cartridge for law enforcement use available today, combining superior stopping power when used with expanding ammunition and manageable recoil into a package that remains compact, even when using a double-stack magazine. The .40 S&W has an overwhelming share of the U.S. law enforcement market as a result. Ironically, a very large part of the law enforcement market for .40 S&W uses GLOCK pistols.

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Case failure reports

The .40 S&W has been noted in a number of cartridge case failures, particularly in GLOCK pistols due to the relatively weak case of the .40 S&W compared to its working pressure, and lack of full chamber support--the feed ramp on the GLOCK .40 S&W pistols are larger than normal, and leaves the rear bottom of the case unsupported, and it is in this unsupported area that the cases fail. Most, but not all, of the failures have occurred with reloaded or remanufactured ammunition. Cartridges loaded to or above the SAAMI pressure, or slightly oversized cases which fire slightly out of battery are often considered to be the cause of these failures. These failures are referred to by many as "kaBooms" or "kB!" for short. While these case failures do not often injure the person holding the pistol, the venting of high pressure gas tends to eject the magazine out of the magazine well in a spectacular fashion, and usually destroys the pistol. In some cases, the barrel will also fail, blowing the top of the chamber off.

While the .40 S&W is far from the only cartridge to suffer from case failures, it is uniquely susceptible for a number of reasons. The .45 ACP is often subject to case failures, especially in the M1911, as ambitious gunsmiths enlarge the feed ramp to improve reliability and leave the case unsupported. This, combined with maximum or greater than maximum pressure loads, is a sure route to a case failure. However, due to the low operating pressure of the .45 ACP, a small amount of unsupported case is not usually a cause for concern. The .40 S&W, on the other hand, works at significantly higher pressures than the .45 ACP. Since the .40 S&W is a very wide cartridge for its length (it was designed to fit in existing 9 mm frames) feed ramps are often steep, and reducing the angle to improve reliability leaves more unsupported case than with a smaller diameter 9 mm or a longer length .45 ACP cartridge.

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External Balistics

8.7 g (135 Gr) Full Metal Jacket: 400 m/s (1310 ft/s) - 696 joules (517 foot pounds) of energy
11.6 g (180 Gr) Full Metal Jacket: 290 m/s (950 ft/s) - 488 joules (363 foot pounds) of energy

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Synonyms

.40
.40 S&W
.40 Auto
.40 Short & Wimpy or Short & Weak (a derogatory comparison to the parent 10 mm Auto cartridge)
.40 Liberty (in the same tradition as "freedom fries," following the widespread boycott of Smith & Wesson in the wake of their anti-gun agreement with the Clinton Administration)
10 mm Kurz

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