You're watching the US military conduct what it claims is the first "successful live-fire tests demonstrating in-flight guidance of .50-caliber bullets." For the uninitiated, .50-caliber rounds are approximately the size of a Sharpie, and are used in long-range sniper rifles and machine guns.
.50-caliber bullets. Image: US Navy, Wikimedia
Now, technology developed by DARPA’s Extreme Accuracy Tasked Ordnance (EXACTO) will transform the projectiles into miniature homing missiles.
The agency explains what you're seeing above: "This video shows EXACTO rounds maneuvering in flight to hit targets that are offset from where the sniper rifle is aimed. EXACTO’s specially designed ammunition and real-time optical guidance system help track and direct projectiles to their targets by compensating for weather, wind, target movement and other factors that could impede successful hits." Here's DARPA's rendering of the projectile:
EXACTO goes into greater detail, noting that "The system combines a maneuverable bullet and a real-time guidance system to track and deliver the projectile to the target, allowing the bullet to change path during flight to compensate for any unexpected factors that may drive it off course."
We've been following the terrifying promise of smart guns for some time, but watching this live fire test was enough to make me spit up my coffee.