The round was developed by Smith & Wesson in 1990 by shortening the casing of the very powerful 10mm Auto. Even though it's only been around for nearly two decades, it has already achieved as much popularity in the US as the 9mm and .45 Auto, which have both been around for over a century.

Basically the round was created to solve a problem that never existed. It was developed to bridge a supposed "gap" between the 9mm and .45 Auto even though both rounds have substantial power as it is. The round appeals to a certain number of semi-auto enthusiasts who are dumb enough to believe that the 9mm is a pee-shooter, yet are too intimidated by the .45 Auto, which only has slightly more recoil. Still, it is a great round for self-defense.
Know-it-all: Don't buy a 9mm for self-defense, I've heard stories of 9mm bouncing off windshields and not being able to take down raging 6' 6" hoodlums on crack. Get a .40.

Me: And can you give me an example of a .40 S&W getting the job done?

Know-it-all: Ummm...no. But 9mm is still wimpy because I said so.
by WALTHERMAN March 24, 2010
A handgun cartridge that is very popular for self-defense and is increasingly being used in police service pistols. Smith and Wesson developed the .40 S&W round off of the 10mm round in order to fill a large gap in stopping power between the 9mm and a .45 ACP. Unlike other rounds, .40 S&W bullets feature a flat tip as opposed to a smooth conical tip as seen in a 9mm. The bullets were designed this way so more surface contact will be made with the bullet's target. The .40 travels at very high velocities, giving the shooter quite a bit of recoil when the gun is fired. However, this additional velocity makes the bullet ideal for shooting through light cover such as car doors or windshields.

Data compiled from police shooting incidents put the .40 S&W at a 96% chance of stopping an attacker with one shot, proving it's value as a formidable defense cartridge. Cheaper than .45 ACP rounds, yet just as effective in getting the job done, the .40 S&W has seen great commercial success.
Guns chambered in .40 S&W are an excellent choice for self-defense.
by Ghost Dog July 12, 2007

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