5.56 NATO is a rimless bottlenecked intermediate cartridge developed in the late 1970s in Belgium by FN Herstal. It was standardized as the second standard service rifle cartridge for NATO forces as well as many non-NATO countries.
Is 5.56 NATO more powerful than 223? The 5.56 NATO has a higher pressure than the 223 round and is one of the two major differences. The 5.56 NATO pressure is about 58,000 psi and the 223 round is approximately 55,000 psi.
Why does the military use 556 and not 223? Differences between the two are small but can have a large impact on performance, safety and weapon function. The first difference is the higher pressure level of the 5.56 NATO cartridge which runs at approximately 58,000 psi. A 223 Remington is loaded to approximately 55,000 psi.
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