I haven't actually done it yet. I was waiting to start until I had all the bits, and I think I just got the last ones today.
You hit the nail on the head with the MR. It is, indeed, too thick. At first I thought I would have a little bit machined off. But then it looks like things with chrome, or plating in general, can be difficult to lathe. And I don't want to waste any machinist's time/equipment on this. So, to be honest, my next approach was going to be to get it in some kind of chuck to hold it straight while rotating, and I'd just take an angle grinder to it to bring the base down so it'll fit in the barrel.