Railgun tech is interesting...but the projectiles are, so far, just envisioned to be solid penetrators. Until they can solve the HE fill and fuzing issues (making a shell that can withstand launch and still function), then these penetrators will not bring much "bang" at the end of their flight. Their velocity will decrease as range increases, lowering their kinetic energy. Maximum range may mean minimum effectiveness. (There is a middle ground, where they may not lose much velocity as they go above most of the atmosphere. Think of the German WWI Paris Gun.) This may create a donut-shaped effectiveness pattern. Good up close, worse in the middle, improving at further distances. That all pre-supposes they cannot solve the construction issues with a filled shell.
Then, as your linked article states, the power requirements are quite high.