I've got a Ballard with a tight chamber and am trying to make up some cases from .405 Winchester.  Neck thickness is .013-.014" I need .008-.009".   

If I send you 20 trimmed and sized cases is there anyone set up to do this?

A forum member suggested neck turning over a mandrel instead.  I might give that a try and see how it works out.  I'm sure I'll destroy a few cases in the process, but I've got 50 Hornaday cases to use in the learning process.

I would also vote for the outside neck turning. Much easier to control the amount of material taken off. Yes a lathe would be faster and easier but if your case does not run true then you run the risk if having the neck thickness out of concentric and that wouldn't be good. Reaming I would think would be the last thing I would consider as your limited on your reamer size 
The only hard part about outside neck turning is finding a cutting setup for that size cartridge. Not many places make tools for much over .35 caliber. 
Sam

The Forrester tool works good.  Little bit off outside turn is the way to go

Boats

Nothing cheap about working with old calibers and guns not built to modern spec. 

If you have a lathe you could take a little off the outside, I have done just that to case bases, off the neck it's probably not going to work as well as with the Forester tool. Of course if you  have a lathe you could use a reamer inside too.

Reamer is cut for one size the little Forester tool I use for many calibers adding pilots as needed, It's really the way to go.

Boats

Here's the reamer that a friend uses to inside the neck ream his cases for .40-70 in his Ballard. It replaces the pilot to ream cases.
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This is to fit a Forster case trimmer, and they are long enough to accept a .40-70 case. He found this one on Ebay in the diameter he needed.

I have used the Forster. It has been a while but if I remember correctly its not too hard to set up and easy to adjust how much you take off the outside of the neck. Hard part is getting the length set. I have only used this on the necks of necked down 30-06 cases that were formed to 6.5. With straight or straight taper cases the hard part will be to figure out just where to stop your cut so that your not cutting into the taper and weakening the case to the point of potential separation.
One thing I don't like is that the hardened pilot that they sell is a very tight fit in the case mouth. If one could make the pilot you could make it a custom fit to your particular case and I think that would make things a little easier in the long run. Also a little lube on the pilot would help too.
Sam

John - sent you a P/M.   I'm set up to turn your necks, but need one piece of data.

Phil