When Navy SEAL snipers fired from a U.S. destroyer and killed three pirates holding an American hostage in a lifeboat 100 feet away, what were the odds of success? Can a sniper reliably hit a human target on a small boat bobbing on the ocean, or were they taking a chance with the hostage's life?
If the pirates' heads were fully exposed, it would have been an easy shot. A sniper rifle is accurate to within a "minute of angle," provided the shooter can keep his or her target in the crosshairs. That means that a good marksman can reliably hit a 1-inch target at 300 feet and reliably kill someone at 3,000 feet. The bobbing of the lifeboat would have been a factor, but snipers regularly shoot at moving targets from moving vehicles. (Advanced Navy SEAL training includes target practice from helicopters.)
There are two techniques for hitting a moving target — trapping, in which the sniper holds the rifle still and waits for the target to move into the sight, and tracking, in which the sniper moves the rifle to keep the target in the sight. Trapping is the easier method and is preferred among less-experienced marksmen.
However, the Navy snipers needed to strike all three pirates simultaneously. Once the countdown began, they could not allow their target to drop from their sight and wait for him to return. (Sniper teams generally count down from five and fire in unison on the T in "two.")
The snipers had other challenges. First, they had to remain stealthy. If the pirates had noticed that gunmen were lying on the destroyer's fantail waiting to pick them off, they never would have exposed themselves to fire. During the day, the SEALs likely used nylon netting to keep themselves in the shadows. Second, they were a little too close for standard sniping tools.
Because the barrel of a rifle sits a couple of inches below the sight, it's angled slightly upward. The center of the sight shows the spot the bullet will hit at 300 feet. At a little more than 100 feet, the SEALs would have had to compensate by aiming slightly above their targets. Finally, the SEALs were shooting from a tall destroyer into a tiny lifeboat, and shooting downward is difficult. A sniper rifle rests on a bipod, and the butt rests against the sniper's shoulder. In order to aim below the level of the bipod, the sniper has to prop his chest up.
Slate thanks William Graves of GPS Defense Sniper School and John Pike of GlobalSecurity.org for sharing their knowledge.