The U.S. Marine Corps has developed a new flechette warhead for use on 70mm (2.75 inch) unguided rockets fired from their helicopters. The new version uses flechettes that are three times the size of earlier ones, inflicting wounds similar to a 5.56mm bullet, and able to penetrate foliage and light armor. In effect, when each 70mm rocket detonates, it propels hundreds of flechettes forward, like a shotgun blast. The rockets are fired in salvos of a up to dozen at a time, enabling a wide area to be covered with flechettes. The new flechette round uses a more effective fuze and firing mechanism, allowing more of the target area to be covered. In effect, the flechette rocket provides the same capability as a burst of machine-gun fire, but the fire is instantaneous, hits targets farther away, and covers a wider area. The larger new, larger flechette also damages vehicles. Initial reports from marine helicopter pilots in Afghanistan indicate that the new flechette rocket works as expected.
The 2.75 inch (70mm) rockets were developed during World War II as an air-to-air weapon for use against heavy bomber formations. The Germans had developed such a successful weapon (the R4M), but before long the Americans noted that neither the Japanese nor the Germans had any heavy bombers, and their rocket weapon was switched to air-to-ground use. Actually, the 70mm rocket was retained for air-to-air use into the 1950s, but it was never successful in that role. The 70mm rocket became very popular in the 1960s, when it was discovered that the weapon worked very well when launched from multiple (7 or 19 tube) launchers mounted on helicopters. The 42-55 inch long rockets could be fired singly or in salvoes, and gave helicopter pilots some airborne artillery for supporting troops on the ground. There many variations in terms of warheads and rocket motors. Some versions can go over 10 kilometers.