905 m/s (2,970 ft/s) 1,679  J (1,238  ft-lbs ) Source: NATO EPVAT testing , QuickLOAD , SAAMI , C.I.P. [ 1 ] 5.56x45mm NATO is a rifle cartridge developed in the United States and originally chambered in the M16 rifle . Under STANAG 4172, it is a standard cartridge for NATO forces as