Two of the most popular cartridges today are nearly identical and sometimes considered transposable, but when looking at 5.56 vs .223, there are some key differences. The .223 Remington started as a ...

For most shooters the difference between .223 Remington and 5.56×45 NATO is minor, but it matters because 5.56 is typically loaded to higher pressures and uses a slightly different chamber leade.