The 3-line rifle, Model 1891 (its official designation at the time) was adopted by the Russian Military in 1891. There have been several variations from the original rifle, the most common being the M1891-30, which was designed in 1930.
When the Soviet Union was invaded by Nazi Germany in 1941 the Mosin–Nagant was the standard issue weapon of Soviet troops. As a result, millions of the rifles were produced and used in World War II by the largest mobilized army in history.
In 1936, the 91/30 was again modified, this time to speed production. The receiver was changed from its octagonal shape to an easier to make round receiver. When war with Germany broke out, the need to produce Mosin Nagants in vast quantities led to a falling-off in finish of the rifles. The wartime Mosins are easily identified by the presence of tool marks and rough finishing that never would have passed the inspectors in peacetime. However, the basic functionality of the Mosins was unimpaired.
By the end of the war, approximately 17.4 million M91/30 rifles had been produced.
In the years after World War II, the Soviet Union ceased production of all Mosin–Nagants and withdrew them from service in favor of the SKS series carbines and eventually the AK series rifles. Despite its growing obsolescence, the Mosin–Nagant saw continued service throughout the Eastern bloc and the rest of the world for many decades to come. Mosin–Nagant rifles and carbines saw service on many fronts of the Cold War, from Korea and Vietnam to Afghanistan and along the Iron Curtain in Europe. They were kept not only as reserve stockpiles, but front-line infantry weapons as well.
Virtually every country that received military aid from the Soviet Union, China, and Eastern Europe during the Cold War used Mosin–Nagants at various times. Middle Eastern countries within the sphere of Soviet influence.
Courtesy of Mosin-Nagant.net and Gunboards.com