5.6×39mm
5.6×39mm is a rifle cartridge or ammunition model.
Also recorded as .220 Russian.
Overview
Ammunition cartridge.
In detail
It is associated with Soviet Union. The record gives 1955 as its date of establishment or first appearance.
Sources
Each source is named with the standing the house places on it, so the evidence can be weighed rather than taken on trust.
reference work · Reputable secondary · Wikipedia
“5.6×39mm”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q3919618: 5.6×39mm
Consult the source