.357 SIG (using Sierra bullets)
Date: Feb 17 2021
The .357 Sig cartridge was a team development between Sig Arms and Federal Cartridge based roughly on the .40 S&W case necked down to accept .355-inch bullets. It was designed to outperform the 9mm Luger—which it easily accomplished—while being chambered in pistols of similar size. It was also intended to more or less duplicate .357 Magnum revolver ballistics using 125-grain bullets. It was formally announced to the public in 1994, and while most bottleneck pistol cartridges have historically had limited acceptance, the .357 Sig has been successful.
Handloading the .357 Sig does pose certain challenges. As indicated, bullets should measure .355 inch (or 9mm), and not the implied .357-inch bullets intended for the .38 Special and .357 Magnum revolver cartridges. Many 9mm bullets are not of correct design to offer reliable function in the .357 Sig. For example, those made to NATO standards often feature a short enough bearing surface on the shank that they fail to provide sufficient case neck tension. As a result, bullets can be deep seated when hitting the feed ramp, which can result in dangerous pressures. Furthermore, they can cause erratic ignition and poor accuracy. As a result, bullet substitutions are not recommended unless they are designed specifically for the .357 Sig, or are of correct design to accommodate the cartridge’s short neck.