Claim: The AK-47 has been used by infantry.

The AK-47 -LRB- -LSB- Автомат Калашникова , translit = Avtomat Kalashnikova , lit = Kalashnikov 's Automatic Rifle -RSB- -RRB- is a selective-fire -LRB- semi-automatic and automatic -RRB- , gas-operated 7.62 × 39 mm assault rifle , developed in the Soviet Union by Mikhail Kalashnikov . It is the originating firearm of the Kalashnikov rifle -LRB- or `` AK '' -RRB- family .   Design work on the AK-47 began in the last year of World War II -LRB- 1945 -RRB- . In 1946 , the AK-47 was presented for official military trials , and in 1948 , the fixed-stock version was introduced into active service with selected units of the Soviet Army . An early development of the design was the AKS -LRB- S -- Skladnoy or `` folding '' -RRB- , which was equipped with an underfolding metal shoulder stock . In the spring of 1949 , the AK-47 was officially accepted by the Soviet Armed Forces and used by the majority of the member states of the Warsaw Pact .   Even after almost seven decades , the model and its variants remain the most popular and widely used assault rifles in the world because of their substantial reliability under harsh conditions , low production costs compared to contemporary Western weapons , availability in virtually every geographic region and ease of use . The AK-47 has been manufactured in many countries and has seen service with armed forces as well as irregular forces worldwide , and was the basis for developing many other types of individual and crew-served firearms . As of 2004 , `` Of the estimated 500 million firearms worldwide , approximately 100 million belong to the Kalashnikov family , three-quarters of which are AK-47s '' .