The comparison between .223 and 5.56 isn’t a new one, so there is a lot of discussion to weed through to learn about the two. Ultimately, because they originated from the same cartridge, they are very similar, but that does not mean that they are necessarily interchangeable. This article discusses three key differences between .223 Remington and 5.56x45mm NATO.

.223 Remington and 5.56x45mm Dimension Measurements

At a glance, the two rounds are indiscernible. Both rounds use a bullet of .224 in in diameter and an overall length of 2.26in. In general, the external dimensions for the two calibers are identical. What’s more significant is the pressure of the two rounds and the difference in the rifle chambering.

.223 Remington and 5.56×45 Pressure Measurements