7.62×39mm in the context of "Calibre"

The AK-47, officially known as the Avtomat Kalashnikova (Russian: Автомат Калашникова, lit. 'Kalashnikov's automatic [rifle]'; also known as the Kalashnikov or just AK), is an assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms designer Mikhail Kalashnikov, it is the originating firearm of the Kalashnikov (or "AK") family of rifles. After more than seven decades since its creation, the AK-47 model and its variants remain one of the most popular and widely used firearms in the world.

Design work on the AK-47 began in 1945. It was presented for official military trials in 1947, and, in 1948, the fixed-stock version was introduced into active service for selected units of the Soviet Army. In early 1949, the AK was officially accepted by the Soviet Armed Forces and used by the majority of the member states of the Warsaw Pact.

An assault rifle is a select fire rifle that uses an intermediate-rifle cartridge and a detachable magazine. Assault rifles were first put into mass production and accepted into widespread service during World War II. The first assault rifle to see major usage was the German StG 44, a development of the earlier Mkb 42. While immediately after World War II, NATO countries were equipped with battle rifles, the development of the M16 rifle during the Vietnam War prompted the adoption of assault rifles by the rest of NATO. By the end of the 20th century, assault rifles had become the standard weapon in most of the world's armies, replacing full-powered rifles and submachine guns in most roles. The two most successful modern assault rifles are the AK-47 and the M16 designs and their derivatives.

The Heckler & Koch HK33 is a 5.56mm assault rifle developed in the 1960s by West German armament manufacturer Heckler & Koch GmbH (H&K), primarily for export.

Building on the success of their G3 design, the company developed a family of small arms (all using the G3 operating principle and basic design concept) consisting of four types of firearms: the first type, chambered in 7.62×51mm NATO; the second, using the Soviet 7.62×39mm M43 round; the third, chambered in .223 Remington and 5.56×45mm NATO; and the fourth type, chambered for the 9×19mm Parabellum pistol cartridge. Commercially the HK33 was a successful design but it did not sell as well as the G3.

The AK-74 (Russian: Автомат Калашникова образца 1974 года, tr. Avtomat Kalashnikova obraztsa 1974 goda, lit. 'Kalashnikov assault rifle model 1974') is an assault rifle designed by small arms designer Mikhail Kalashnikov in 1974 as a successor to the AKM. While primarily associated with the Soviet Union, it has been used by many countries since the 1970s. It is chambered for the 5.45×39mm cartridge, which replaced the 7.62×39mm cartridge of Kalashnikov's earlier automatic weapons for the Soviet Armed Forces.

The rifle first saw service with Soviet forces in the Soviet–Afghan War from 1979. The head of the Afghan bureau of the Inter-Services Intelligence (ISI), the intelligence agency of Pakistan, claimed that the American Central Intelligence Agency (CIA) paid $5,000 for the first AK-74 captured by the Afghan mujahideen during the war.

A full metal jacket (FMJ) bullet is a small-arms projectile consisting of a soft core (often lead) encased in an outer shell ("jacket") of harder metal, such as gilding metal, cupronickel, or, less commonly, a steel alloy. A bullet jacket usually allows higher muzzle velocities than a lead alloy cast bullet without depositing significant amounts of metal in the bore. It also prevents damage to bores from hard steel or armor-piercing core materials.

The Type 56 (Chinese: 56式自動步槍, lit. 'Type 56 automatic rifle') is a Chinese 7.62×39mm assault rifle and Kalashnikov rifle variant.