A good eye and a file would do it. We're only talking about removing 18 thou here anyway, on kuduae's figures.
Good occupational therapy in front of the telly!

The penalty for slightly out-of-round rims is nothing in real terms.

Chucking the case-neck in a drill press (or even a power-drill) on a mandrel (seated projectile?) could speed-up the process and reduce errors, but with the case body unsupported one would need to be gentle with file pressure.

Of course a lathe is better...