The 5.56Γ45mm NATO (official NATO nomenclature 5.56 NATO, commonly pronounced "five-five-six") is a rimless bottlenecked centerfire 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 identical, the 5.56Γ45mm NATO cartridge family was derived from the .223 Remington cartridge designed by Remington Arms in the early 1960s, which has a near-identical case. However, firing chamber dimensions differ slightly between rifles manufactured for the designated cartridges. The differences may cause unsafe chamber pressures when firing 5.56 NATO in rifles designed for .223 Remington. Therefore, this combination is not recommended.