Well Artfull,
One way or another there is still the purchase of a reamer involved.
As Pacific tool can grind what ever you want at no extra cost, it would be better to have the proper reamer with the RIM.
With a standard reamer the job can be done, but anyway you have to either build a jig or solder the martini extractor onto the barrel and cut the rim with a lathe tool.
Just my thought.
Nick