Instead of firing its bullets with noisy explosions, a silent machine gun, invented by William B. Hale and Durand Beam, shoots with compressed-air power. In recent tests the rifle, which resembles a sub-machine gun, discharged 10,000 shots a minute, reducing three-inch oak planks to kindling and turning airplane armor plate into steel mosquito netting. As firing starts, the barrel cools, instead of heating, due to use of air as the propelling power.