DARPA’s Extreme Accuracy Tasked Ordnance (EXACTO) program has produced a bullet that can somehow steer itself after it’s fired, tracking what looks like a laser (or other optical designator) towards a target that can be “moving and evading.” This allows an experienced shooter to consistently and reliably hit very difficult targets, and as the video shows, even a novice can hit a moving target at long range on the first try.
The key differentiator here is that since the bullets are self-steering, they can be controlled
after they leave the barrel of the gun, which hasn’t been possible until very recently. Systems like
TrackingPoint’s precision-guided rifle and scope use lasers and computer vision to autonomously lock on to targets and will even fire the rifle for you, but no matter how fancy your aiming system is, a downrange crosswind or a target that changes direction after you fire is impossible to compensate for: once you’ve pulled the trigger, all you can do is watch what happens. But with EXACTO, as long as you keep a laser dot on whatever you’re aiming at, the bullet will steer itself there.
At this point, it’s not entirely clear just how, exactly, DARPA’s bullets do what they do, probably because it’s highly classified.
Sandia National Labs demonstrated an optically guided steerable bullet a few years ago that uses fins, but it had to be fired from a special smooth bore rifle. DARPA's bullets can be fired from a standard .50 caliber weapon, suggesting that they can steer themselves while spinning, which is quite a trick.