The Next Generation Squad Weapon (NGSW) program is a United States military program created in 2017 by the U.S. Army to replace the 5.56mm M4 carbine, the M249 SAW light machine gun, and the 7.62mm M240 machine gun, with a common system of 6.8mm cartridges and to develop small arms fire-control systems for the new weapons.

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.