[krapp]

The story that I read somewhere was that it was tested once but the recoil either damaged the station or it would have affected its orbit so they never tried it again.

There was also Polyus which was going to be an entire battle station designed to counter Reagan's SDI satellites[0], but it never made it into orbit. It had lasers, though.

[0]https://nationalinterest.org/feature/the-rise-fall-the-sovie...

[necovek]

If that test round of bullets came out at 1000m/s, I wonder where are they now?

They'd cover around 1.5 billion km (<1 billion miles), and be past Saturn's orbit if fired away from the Sun. But it would not achieve escape velocity on its own, and the station was obviously moving relative to Sun and Earth, so we'd have to account for it too.