Rifle, Caliber 5.56mm, M16. No other firearm has served with the United States military for so long. Designed by Eugene Stoner working for Armalite, the weapon was revolutionary. The use of polymers and aluminum in its construction was pioneered in the earlier AR-10, while the new rife, known as AR-15, would fire the .223 Remington, a small-caliber high-velocity cartridge that offered great stopping power and accuracy for little recoil and small size.

In 1964, the AR-15 would be accepted into US service as the M16, its cartridge subsequently standardized by NATO as the 5.56x45mm NATO. Despite its rough beginnings in the jungles of Vietnam, it was soon molded into a light, reliable, and adaptable weapon, and served to validate the concept of small-caliber, high-velocity bullets.

Even after 50 years of its introduction, the M16 and variants remain popular with both military and civilian customers because of the aforementioned reasons. Within SimplePlanes, it is the primary service rifle of the Paternian Republic, although it has largely been supplanted by the M4, a carbine derivative.