The .220 Russian (5.6x39mm) cartridge was developed in the late 1950s for deer hunting in Russia. It is a 7.62x39 cartridge necked down to hold a 5.6mm bullet. It was later adopted by Finland, and by around 1965 was being produced by SAKO and Lapua. When it was introduced to the United States, Sako, and later Lapua, brass was stamped ".220 Russian". This round was notably used in the TKB-022PM5 bullpup assault rifle and development of the standard issue 5.45x39mm round.
The .220 Russian is the parent case for the .22 PPC and the 6 mm PPC cartridge.