http://www.sciscoop.com/story/2003/11/3/171841/084 The M1A1 Abrams tank is widely acknowledged to be the best tank in the world. It weighs just shy of 70 tons and much of that weight is armor to protect the vehicle and its crew. There are two main threats against a tank: HEAT (High Explosive Anti-Tank) rounds and KE (Kinetic Energy) rounds. To greatly oversimplify, HEAT rounds produce a blob of super-hot molten metal that cuts through armor like a torch; KE rounds have long, slender dart-like projectiles that punch through armor like a bullet. The structural armor of the tank is designed to stop KE rounds...