5.56 x 45mm NATO (.223 Win)

The .223 is used by law enforcement agencies more than the .308 because they fear over penetration (the bullet might hit a hostage standing behind the gunman). One impact, the .223 splinters so over penetration isn't likely. Since the .223 has a lack of penetration and is not very accurate on a windy day, only use it for head shots when possible. Click here for more information on the .223 round, page by Hitach Industries, Inc.

The 5.56AP round will penetrate 12 mm of armor plate of 300 HB at 100 meters.

The US Army uses the M855 and M856 in their M249 SAW, due to its effectiveness against body armour and helmets. It is designed to function properly in all 5.56mm weapons with a 1 in 7 barrel twist.