Russian-small-arms enthusiasts will be pretty excited to watch the below video; trigger time on the PSM deep-concealment handgun, a pistol virtually unknown in the US as it is too small to comply with ATF import regulations (a similar obstacle prevents the importation of true Walther PPKs). Larry Vickers walks us through shooting the gun, which is chambered for a unique 5.45×18 caliber, capable of penetrating light body armor, while being in the same class as the .32 ACP:

The 5.45x18mm cartridge actually pre-dates the introduction of the larger 5.45x39mm rifle caliber that shares its name. However, the bore diameter of the 5.45x18mm caliber is slightly larger than that of the 5.45x39mm, and so far as I know the two calibers are not related to each other in any meaningful way.

The PSM handgun was designed as a concealed weapon for VIPs, dignitaries, and plainclothes agents, who might need to kill an attacker wearing body armor. While not as small in dimensions to some more modern guns in larger calibers, it is very thin, at about three-quarters of an inch. The small-diameter 5.45x18mm cartridge is key to both of these requirements, as it’s projectile has low frontal area, enhancing penetration.