The U.S. Army is trying to replace the 60 ton M-1 tank with a vehicle weighing half as much. Both will use a 120mm gun. But the one for the lighter FCS (Future Combat System) vehicle, the XM360, is a third lighter (two tons, versus three tons) than the one used in the M-1. The XM360 uses a lot of new materials and design innovations to cut the weight. But further tweaks have reduced the recoil from 70 tons to 43 tons. That makes it possible to mount the gun in a much lighter vehicle. So far, all the testing and development of the XM360 has been done with the gun itself. It will be another three years before an XM360, mounted in the FCS vehicle, will roll out and open fire.

The MCS tank will use more technology in its fire-control system. More computers and sensors, which will make it possible to achieve more first round hits at targets up to 12 kilometers away (three times the range of current M-1 120mm ammo). That's with new ammo. Using the same shells the M-1 currently uses, the XM360 will be more accurate at 4 kilometers, mainly because of the new fire control gear (which can also be installed in the M-1). The XM360 also uses an auto-loader, something the Russians have been using since the 1960s.

Giving a lighter vehicle similar protection to the current M-1 tank is a major challenge, and most observers want to see it work before they buy into it.