While often used interchangeably, the .223 Remington and 5.56mm NATO are not the same cartridge. The .223 Remington served as the basis for the 5.56mm NATO, they are *not* the same cartridge. The 5.56mm NATO round fires at much higher velocities than the .223 Remington. The same applies to the .308 Winchester served as the basis for the 7.62mm NATO round, but again, they are not the same cartridge. Aside from offering a little clarification, my point is this: choosing armor rated for the 5.56mm NATO and/or 7.62mm NATO is the better course of action. The reason being: armor that can stop .223 Remington *may not* stop 5.56 NATO, and armor that can stop .308 Winchester *may not* stop 7.62 NATO.