September 17, 2013:
The U.S. 120mm M829A3 anti-tank shell is now available in a version using tungsten for the penetrator instead of depleted uranium. This is for buyers who are upset about all the media angst about how dangerous depleted uranium is (it isn’t, at least no more so than tungsten). The M829A3 weighs 22.3 kg (49 pounds), is 892mm (35 inches) long, and uses 8.1 kg (18 pounds) of slow burning explosives to propel the shell out the 120mm smooth barrel to a top speed of 1,555 meters (5,100 feet) a second. The sabots fall away after the shell leaves the barrel, leaving the 10 kg (22 pound), 25mm diameter (and 800mm long) depleted uranium or tungsten penetrator to continue on to the target (up to 5,000 meters).
Most modern 120mm tank guns fire a shell that uses a smaller 25mm “penetrator.” The 25mm rod of tungsten (or depleted uranium) is surrounded by a “sabot” that falls away once the shell clears the barrel. This gives the penetrator higher velocity and penetrating power. This is the most expensive type of 120mm shell and already comes in several variants. There is APDS (Armor Piercing Discarding Sabot) and APFSDS (Armor Piercing Fin Stabilized Discarding Sabot, for smooth bore guns). The armor piercing element of discarding sabot rounds is less than half the diameter of the shell and made of very expensive, high density metal. Its smaller size enables it to hit the target at very high speeds, up to 1,900 meters (5,900 feet) a second. This is the most common type of anti-tank shell and is constantly being improved.
In the 1970s depleted (nonradioactive) uranium was introduced by the U.S. for penetrators. Most armies now have 120 mm and 125mm smoothbore guns which can obtain slightly more penetrating power using depleted uranium instead of tungsten. Composite armor was developed to defeat APDS but it was not always successful. HEAT (High Explosive Anti Tank) rounds have fallen from favor because their success depends on hitting a flat surface on the tank. Modern tanks have few flat surfaces. On the plus side, HEAT shells must be fired at lower speeds, are good at any range, and many are now built with a fragmentation capability to make them useful for anti-personnel work. The AP type shells are less effective at longer ranges. Similar to HEAT, more expensive and still in use, is the HESH (High Explosive Squash Head) shell. This item hits the tank, the explosive warhead squashes, and then explodes. The force of the explosion goes through the armor and causes things to come lose and fly about the inside of the tank (the spall effect). The vehicle may appear unharmed, but the crew and much of its equipment are not. Works at any range but is somewhat defeated by spaced and composite armor.
Then there is the controversy over the health issues associated with depleted uranium, which is a metal that is one of the heaviest known. It is very effective at punching holes through enemy tanks. It is so named because all the harmful radiation has been "depleted" from it as a by-product of manufacturing nuclear fuel. But because it's still considered a "nuclear" material it is controlled by the U.S. Nuclear Regulatory Commission. In effect, these anti-tank shells are technically "nuclear weapons." U.S. export laws had to be changed to allow the export of depleted uranium ammo.
Early on there were rumors that depleted uranium created dangerous levels of radiation when handled or used. In reality, depleted uranium is no more toxic than tungsten and other heavy metals. It is true that when depleted uranium penetrators go through armor, and come under enormous stress, they do produce brief, but high, bursts of radiation. This seems to be because a chunk of depleted uranium will absorb most of the radiation it produces through normal decay, which it cannot do once shattered. However, it is unlikely that the resulting "pulse" of radiation will cause injury or illness, particularly given the damage produced by the explosive effect and shell fragments inside a vehicle hit.