Railgun range in space.... Infinite (or until it hits something). There is no friction to slow it down, no gravity of sorts to bring it back down (until it meets something)
The extreme coldness of space is also the perfect solution to using it in space, and should help with "The heat generated in use makes a rail gun beyond our capacity to be used more than a few times between rebuilds."
If the source posted by the op, claiming that Satellites are powerful enough to knock a object off course, then i'm sure the kinetic force of a Railgun is just as good, if not better.
And in case you're not the most observant of members, i did put "Shame that's pretty much Sci-Fi at the moment." in my initial post.
(And... we where both wrong about the velocity speed of the projectile, it's currently 5,637mph, but, ahh well)

