Glock G31 Gen4

About the Glock G31 Gen4

The Glock G31 Gen4 is the fourth-generation variant of Glock's full-size .357 SIG duty pistol, featuring Gen4 improvements applied to the high-velocity law enforcement platform. Built on the same full-size frame as the Glock 17 and 22, the G31 Gen4 delivers 15+1 rounds of .357 SIG -- a bottleneck cartridge designed to replicate .357 Magnum ballistics in a semi-automatic pistol. The Gen4 adds modular backstraps for customizable grip fit, a dual recoil spring assembly that helps manage the .357 SIG's sharp recoil impulse, a reversible enlarged magazine catch, and the Rough Textured Frame for enhanced grip. With a 4.49-inch (114mm) barrel, the G31 Gen4 propels 125-grain bullets at approximately 1,410 fps (430 m/s) for 748 joules of muzzle energy, providing exceptional barrier penetration capability. Weighing 26.10 ounces (740g) with an empty magazine, the G31 Gen4 was widely adopted by state police and highway patrol agencies that valued the .357 SIG's performance against automotive glass and intermediate barriers.

The G31 Gen4 represented the zenith of the .357 SIG's law enforcement era. State police agencies across America -- Virginia, Delaware, Texas, North Carolina -- standardized on the platform, valuing its ability to defeat car windshields and door panels that could stop conventional handgun rounds. The Gen4's modular backstraps were a welcome addition for agencies with diverse officer hand sizes. When the FBI's 2014 study concluded that modern 9mm defensive ammunition had closed the performance gap with larger calibers, the .357 SIG's days as a mainstream law enforcement round were numbered, making the G31 Gen4 the final chapter of an era.

Glock G31 Gen4 specifications

The G31 Gen4 shares identical external dimensions with the Glock 22 Gen4 (.40 S&W) and can be converted between calibers with a barrel swap, since the .357 SIG is a necked-down .40 S&W case. Weight without magazine is 660g (23.28 oz). The Gen4 dual recoil spring was particularly beneficial for the .357 SIG, as the cartridge's higher operating pressure produces a sharper recoil impulse than .40 S&W. The .357 SIG's bottleneck case design provides extremely reliable feeding. The G31 Gen4 has been discontinued as the .357 SIG market has contracted with many agencies transitioning back to 9mm following the FBI's 2014 ammunition study. Compatible with G22 .40 S&W magazines (same magazine body, different feed lips).