The U.S. has successfully tested a new 120mm tank round that can use either laser designation, or an image recognition radar, to find its target. The tests so far have only hit targets 8,000 meters out. The XM-1111 MRM (Mid Range Munition) round is to eventually be able to hit targets 12,000 meters away, using either radar or laser guidance. Two methods are desired because lasers can be degraded in mist, rain or dust storms. The XM-1111 shell uses low speed to approach and find the target, then fires a rocket to achieve bullet type speed to penetrate the target with a small diameter penetrator made of very dense metal (like depleted uranium). Thus the XM1111 is fundamentally different from current missiles of the same type, which are subsonic and always use a shaped charge warhead.
There is also a version of the XM1111 with a shaped charge warhead, and this is for shots beyond what the tank gunner can see (about 6,000 meters.) This CE (Chemical Energy, as opposed to KE, or kinetic energy) version is fired at and upward angle and as it comes down, its radar seeks out objects that resemble a tank (using images stored in the warhead memory).
The earliest U.S. tank missile was the U.S. MGM-51 Shillelagh. This was a 60 pound, 152mm missile developed fifty years ago. Guidance technology back then was crude, using infrared signals that required the gunner to keep his sights on the target until the subsonic missile hit. Range was 2,000 meters. The Shillelagh system used a short barrel and could fire a howitzer type round as well. The weapon was used on the Sheridan light tank and a few M60 tanks. Some 80,000 Shillelagh missiles were built, and only two were fired in combat (in 1991). The U.S. found high speed, 105mm and 120mm tank rounds were more effective, and dropped Shillelagh type weapons.
Russia, however, went on, and by the 1980s had a missile with a range of 4,000 meters and about the same accuracy as the Shillelagh. These missile systems are expensive, but the Russians continue to turn them out, and China has copied some of the designs. Russia currently has the 9M119M "Refleks-M" (or AT-11) in service. This is a 53 pound system that launches a 38 pound missile (with a ten pound warhead) at targets up to 5,000 meters away. The warhead can penetrate up to 750mm of armor using a shaped charge. Guidance is via a laser, which is aimed at the target. None of these Russian systems have been used in combat with any great success.
Israel produces the Lahat, which can be fired from 105mm and 120mm tank barrels. This is a 27 pound missile, similar to the Russian "Refleks-M", but with a range of 8,000 meters. Lahat also uses laser guidance, but has the ability to fly over the tank and detonate a shaped charge warhead that will punch through the thinner top armor. There is also a version of Lahat that can be used by UAVs. This one has a range of 13,000 meters. This system consists of a 165 pound launcher (including four missiles).
Weight and price of the XM-1111 have not been nailed down yet. Both will likely be higher than the Russian and Israeli weapons. Thus the XM-1111 will probably weigh over a hundred pounds, cost over $100,000 per round and be ready for service in about three years. The army is spending about $300 million to develop the XM1111.