5.56 is a high velocity, small caliber intermediate rifle cartridge developed in the United States and originally chambered in the M16 rifle, however it is also a a general-purpose round used in many light machine guns as well. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries. It is derived from, but not identical to, the .223 Remington varmint cartridge. 5.56mm is common, light, cheap, easy to make, however, has very poor stopping power. As a result, 5.56 has received heated criticism for its poor performance on the battlefield, largely from soldiers. Criticism began in the Vietnam War when soldiers had to fight against the far more powerful 7.62 AK-47.