The SA80 is a British family of 5.56×45mm NATO service weapons used by the British Army. The L85 Rifle variant has been the standard issue service rifle of the British Armed Forces since 1987, replacing the L1A1 Self-Loading Rifle. The prototypes were created in 1976, with production of the A1 variant starting in 1985 and ending in 1994. The A2 variant came to be as the result of a significant upgrade in the early 2000s by Heckler & Koch and remains in service as of 2023. The A3 variant was first issued in 2018 with several new improvements.

The 5.56×45mm NATO is a rimless bottlenecked intermediate cartridge family developed in the late 1970s in Belgium by FN Herstal. It consists of the SS109, L110, and SS111 cartridges. On 28 October 1980, under STANAG 4172, it was standardized as the second standard service rifle cartridge for NATO forces as well as many non-NATO countries. Though they are not entirely identical, the 5.56×45mm NATO cartridge family was derived from and is dimensionally similar to the .223 Remington cartridge designed by Remington Arms in the early 1960s.