SIG-SAUER introduced the .357 SIG in 1994 with Federal Premium Ammunition. The intent behind developing the cartridge was to have the power of the .357 Magnum available in a rimless cartridge, and be used specifically in semi auto pistols. The 125 grain .357 Magnum bullet was a self-defense round with years of proven effectiveness. The cartridge had routinely been issued by police agencies for their service revolvers, but the growing popularity of 9mm and .40 S&W for semi-automatic pistols gradually pushed the .357 Magnum out of law enforcement circles.
Hence the .357 SIG. The case of this cartridge is based on the case for a .40 S&W, but is necked down to accept 0.355" bullets. This case holds enough powder to generate the necessary pressures to propel a 125 grain bullet over 1,350 feet per second. Muzzle energy exceed 500 foot pounds, truly superior performance that puts the .357 SIG in the same league as the .357 Magnum when firing 125 grain bullets.
The .357 SIG is designed specifically to be used in semi-auto pistols, a big advantage that permits the cartridge to be fired in a .40 S&W pistol just by changing the barrel. Additionally, the recoil of the cartridge is comparable to the .40 S&W, which is significantly less than the .357 Magnum, which the .357 SIG was designed to emulate.
The .357 SIG is not the most popular law enforcement handgun cartridge, but the .357 SIG is issued by several prominent police agencies as their sidearm cartridge. The first major law enforcement agency to issue the .357 SIG for duty was the Texas Highway Patrol in 1995. The Secret Service, Bureau of Industry and Security and Air Marshals are federal agencies which use the .357 SIG. State law enforcement agencies that used the .357 SIG in the past, or are currently using it in their duty pistols include: Delaware, Mississippi, Montana, New Mexico, North Carolina, Oklahoma, Rhode Island, Tennessee, Texas and Virginia. Many other county and city level agencies have also adopted the .357 SIG. Most agencies use SIG-SAUER pistols, but many others use the Glock 31.
The .357 Magnum has more data than the .357 SIG that records performance of the cartridge in defensive shooting situations, but the data this is available shows that the .357 SIG is just as capable as the .357 Magnum. The .357 SIG is expected serve both law enforcement and civilian users for a long time to come.