Depends on the whatever.
A typewriter, flung from that height, would burn up. If someone drops a safe on your head, even from the moon, it's going to be a bad day for you.
The point is, the math calculations to be able to hit a specific target, five days in the future, is a bit more complicated than figuring out what shape and weight to use to get an effective artificial meteor.
The precision and stability necessary to make an accurate rail gun while shooting through a randomly moving atmosphere is a hugely sophisticated project. Thermal stability alone would be very troubling. IMO, it would be unlikely to be any more than a weapon of terror. Even if they could do all that, there would be a long period of "fire for effect," during which its location and purpose would be established with which to justify and execute retaliation. It would be a very expensive fixed target that would take very little to render useless.