The US military has been testing in-flight guidance for .50-caliber bullets, turning the projectiles into miniature homing missiles.

DARPA's Extreme Accuracy Tasked Ordnance (EXACTO) bullets have the ability to maneuver in flight to hit targets that they're not precisely aimed at, compensating for factors like weather, wind, and target movement.

DARPA explains on its website: "For military snipers, acquiring moving targets in unfavorable conditions, such as high winds and dusty terrain commonly found in Afghanistan, is extremely challenging with current technology. It is critical that snipers be able to engage targets faster, and with better accuracy, since any shot that doesn't hit a target also risks the safety of troops by indicating their presence and potentially exposing their location."

The bullets are the size of a large pen and can be used in both sniper rifles and machine guns. The full EXACTO system comprises of both bullets and a real-time guidance system that tracks and delivers the projectile to the target.

They're still some way from the battlefield, however. This live fire test is likely just the first of many.

This story originally appeared on Wired UK.