The lineage of the 5.45 x 39mm rifle round that is commonly found in the AK-74 rifles all around the world can in a weird way trace its lineage back to the 5.56 x 45mm that NATO and the United States Military uses. Way back in the 1950’s what was then known as the Soviet Union had a fairly extensive network of spies and moles in almost every aspect of American society. In the years since the collapse of the Soviet Union in 1991 the full extent of the espionage rings are just coming to light. It was through one of these networks that the Soviets learned of the United States development of a new main battle rifle to replace the short-lived Springfield M-14. This new rifle which became the Armalite/Colt M-16 as we know was chambered in the newly developed 5.56 x 45mm cartridge. This apparently made the Soviet Union paranoid that they were missing out as they watched their chief rival adopt an ideology of soldiers carrying smaller, lighter rifles that shot a smaller lighter bullet. This fact also let people carry more rounds per person into combat, and the Soviets were not about to take that fact lying down.
The Process of Design
Over the next decade the Soviets built teams of engineers to try to design a Soviet designed round that would replicate the 5.56 x 45mm in terms of accuracy and ballistics yet still use the AK-47 as its weapons platform. In 1967 the Soviet Union finally came up with a test design and the first 5.45 x 39mm cartridge using the newly devised lacquer coated steel cased ammunition was approved for testing. A few years later the team led by renowned Soviet weapons designer V.M. Sabelnikov had the now infamous and banned from importation “Standard” 5.45 x 39mm cartridge known as 7n6 approved for mass production by the Kremlin.
During this process the new rifle chambered in the 5.45 x 39mm operated and looked almost identical to the standard issue AK-47 which was formally adopted in 1947. So in typical drab plain Soviet fashion for the time the new rifle adopted in 1974 would be known as the AK-74. While not overly original or complicated, the Soviet numbering system was simple and easy to follow. The engineering team behind the AK-74 and 7n6 cartridge didn’t just sit back and rest, they went to work on developing a full complement of other times of ammunition for the newly minted AK-74 rifle. In short time the various design teams had successfully developed tracer rounds (7T3), training rounds (7×4), as well as a reduced velocity rounds (7U1) and blank rounds (7×3).