The 5.56mm bullet is a small caliber projectile commonly used in military and law enforcement applications. It was originally developed by the United States military in the 1960s as a replacement for the larger, heavier 7.62mm round. The 5.56mm bullet is lightweight, fast, and accurate, making it ideal for use in small arms such as rifles and carbines.

The bullet itself measures 5.56mm in diameter and is typically made from copper or copper alloys, with a lead core. It is designed to be fired at high velocities, with muzzle velocities ranging from 2,700 to 3,300 feet per second. This high velocity allows the bullet to maintain its stability over long distances, making it effective at ranges of up to 600 meters. While the 5.56mm bullet is not as powerful as larger caliber rounds, it is designed to penetrate body armor and cause significant tissue damage, making it a popular choice for military and law enforcement personnel.