The March 4th Battle of Roberts Ridge in Afghanistan featured a rare use of cannon for ground support. Not the 30mm cannon of the A-10, but the 20mm air-to-air cannon of F-15s and F-16s. These aircraft still carry these multi-barrel weapons, along with about 500 rounds of ammunition. The explosive shells have an effective range of about 1600 meters and are fired at the rate of 100 shells a second. In other words, the pilot has 4-5 bursts of cannon fire. On Roberts Ridge, the al Qaeda fighters were so close to U.S. troops, that the air force controller on the ground decided to have the two F-15s in the area use their cannon first. The controller carefully explained where the al Qaeda were, and the first F-15 had to make several passes before he was sure he knew where the enemy and friendly troops were. But when the two F-15s, and later two F-16s (with the same 20mm cannon as the F-15), opened fire, it was to good effect. All four aircraft used their 2,000 rounds of ammo to knock back the al Qaeda, and later finished off the job with 500 pound laser guided bombs. The al Qaeda bunker in the area was finished off by a Hellfire missile from a CIA UAV. Using an aircraft like the F-15 to strafe ground targets is a tricky business, especially in the mountains of Afghanistan. At it's slowest speed, the F-15 is till going to be moving at about 100 meters a second. Doesn't leave much room for error.