Both the M16 and the M4 version of it are in caliber 5.56mm x
45mm. Likewise, the Heckler & Koch HK416 - which may be what
you meant to refer to - is also is 5.56x45.
Both the M16 and the M4 version of it are in caliber 5.56mm x
45mm. Likewise, the Heckler & Koch HK416 - which may be what
you meant to refer to - is also is 5.56x45.