The 5.45x18mm is a Soviet handgun cartridge developed around 1969-1970. It has seen use by Russian police, military and the KGB since 1973. It is utilized in the PSM Pistol as well as the OTs-23 Drotik machine pistol.
One interesting aspect of this cartridge is how it uses a spitzer-style bullet, which is atypical of most handgun ammunition. There are several wildcat cartridges that are very similar to the 5.45x including the .224 Montgomery and the .22 Epperson Cricket, both of which are .25 ACP cases necked down to accept a spitzer-style .224 caliber bullet.
The 5.45x18mm cartridge fires a 38.6 grain bullet