When it comes to the 223 vs 556, it’s not so much about which one is best, but about the differences between them. The 223 Remington and 5.56 NATO cartridges have identical case dimensions but are not ...

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.

Some believe the 5.56 NATO was the original military cartridge and that the 223 Remington was the civilian offshoot. That’s not the case. In 1970, NATO (North Atlantic Treaty Organization) affiliated ...