craigd,
You are correct all the way around. That is precisely how I do it for my cases. I milled the first one in half, and there is enough web. I set the lathe up with "stops" and make a production of it. The stops makes it precise enough. The only thing I do "by hand" is chamfer the newly uniformed primer pocket. I found doing that under power with a handheld tool , made it too easy to take out too much allowing gas leakage. Another benefit is the now incorrect headstamp is removed.
Mike