Although slow and expensive, railgun tanks can deal massive damage from long distance. It is good vs mid-ranged units, but can tear apart any units with ease when sufficient number of them are gathered in a base with defense grid support. The only way to counter these high-tech tanks are with bombing run on the defense grid, followed by suicide runs of fast units like hammerheads and hellfires with mixed army following closely behind. Also to build these units you need titanium and uranium and take up to 50-60 minutes to build depending on your allaince training speed upgrades.