<P> The AK - 47, or AK as it is officially known (Russian: Автома́т Кала́шникова, tr . Avtomát Kaláshnikova, lit . Kalashnikov's Automatic Rifle), also known as the Kalashnikov, is a gas - operated, 7.62 × 39mm assault rifle, developed in the Soviet Union by Mikhail Kalashnikov . It is the originating firearm of the Kalashnikov rifle (or "AK") family . </P> <P> Design work on the AK - 47 began in 1945 . 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 (S--Skladnoy or "folding"), which was equipped with an underfolding metal shoulder stock . In early 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 . </P> <P> 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 and insurgencies worldwide, and was the basis for developing many other types of individual, crew - served and specialised 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". </P> <P> During World War II, the Sturmgewehr 44 assault rifle used by German forces made a deep impression on their Soviet counterparts . The select - fire rifle was chambered for a new intermediate cartridge, the 7.92 × 33mm Kurz, and combined the firepower of a submachine gun with the range and accuracy of a rifle . On 15 July 1943, an earlier model of the Sturmgewehr was demonstrated before the People's Commissariat of Arms of the USSR . The Soviets were impressed with the weapon and immediately set about developing an intermediate caliber fully automatic rifle of their own, to replace the PPSh - 41 submachine guns and outdated Mosin--Nagant bolt - action rifles that armed most of the Soviet Army . </P>

How many ak47s are there in the us