.223 Remington vs 5.56 NATO: Know the Difference Before You Fire .223 and 5.56 NATO History of 5.56 NATO: The 5.56×45mm NATO (often called “five-five-six”) is a type of bullet used in military rifles. It was created in the late 1970s in Belgium by a company called FN Herstal. This bullet family includes types called SS109, L110, and SS111. On October 28, 1980, NATO (a group of countries that work together on defence) officially chose it as one of their standard bullets for rifles. Many other countries outside NATO also use it. The 5.56 NATO bullet is based on an older bullet called the .223 Remington, which was made in the early 1960s by Remington Arms. These two bullets look very similar, but the 5.56 NATO fires a slightly bigger bullet and is built for military use. History of .223 Remington: The .223 Remington (often said as “two-two-three”) is a type of bullet. It has a rimless, bottlenecked shape and uses centrefire ignition, which is common in rifle bul...