What is the difference between a .223 round and a 5.56 NATO round?

Shank (.223 Remington) - 0.4370 / (NATO 5.56) - 0.4370 / (Difference) - 0.0000

Base Diameter (.223 Remington) - 0.3760 / (NATO 5.56) - 0.3780 / (Difference) - 0.0020

Shoulder Diameter (.223 Remington) - 0.3553 / (NATO 5.56) - 0.3560 / (Difference) - 0.0007

Neck-2 (.223 Remington) - 0.2550 / (NATO 5.56) - 0.2550 / (Difference) - 0.0000

Neck-2/Case Mouth (.223 Remington) - 0.2540 / (NATO 5.56) - 0.2550 / (Difference) - 0.0010

Freebore Diameter (.223 Remington) - 0.2245 / (NATO 5.56) - 0.2270 / (Difference) - 0.0025

Pilot Diameter (.223 Remington) - 0.2180 / (NATO 5.56) - 0.2180 / (Difference) - 0.0000

Base-to-Case Mouth (.223 Remington) - 1.7720 / (NATO 5.56) - 1.7750 / (Difference) - 0.0030

Base-to-Shoulder (.223 Remington) - 1.2340 / (NATO 5.56) - 1.2380 / (Difference) - 0.0040

Neck Length (.223 Remington) - 0.2200 / (NATO 5.56) - 0.2180 / (Difference) - -0.0020

Freebore Length (.223 Remington) - 0.0250 / (NATO 5.56) - 0.0500 / (Difference) - 0.0250

Rim/Belt Thickness (.223 Remington) - 0.2000 / (NATO 5.56) - 0.2000 / (Difference) - 0.0000

Shoulder Angle (Degrees) (.223 Remington) - 23.0 / (NATO 5.56) - 23.0 / (Difference) - 0.0

Throat Angle (Degrees) (.223 Remington) - 3.1 / (NATO 5.56) - 2.5 / (Difference) - -0.6