HK421 with ‘para' stock and 330 mm barrel. For illustrative purposes. (Janes/ Amael Kotlarski) Heckler & Koch (H&K) is currently developing a 5.56×45 mm version of the HK421 light machine gun ...

But they aren’t exactly the same. Here’s how they are different and what you need to know on 5.56 vs .223. A sampling of the 5.56 ammo we tested. Tyler Freel Though the 5.56mm NATO and .223 Remington ...