Thanks again for the replies.
First of all, single shot chambering is what I do with most all of my rifles. The Savages usually have enough leade to place longish bullets close to the rifling. Even on my AR-15 (Colt HBar), I use a nylon device that holds the bolt open after each shot when using long, heavy bullets, which it really likes. All the Axis rifles, have extra mags which I have converted into single shot mags.

I won't need a reamer, INHO. If you look at the drawings for the .221 versus the .223, you will see that the shoulder angle, neck, etc is identical.
The only difference is that the .221 has a few thousands less body taper near the shoulder. Playing with one of the Axis rifles with a COL tool, shows that fully sized .221 brass will indeed headspace on the shoulder of the .223 chamber.
Even if it didn't, there is a simple alternative. Simply shorten a .223 sizing die.
I'm doing this because of the challenge. ha ha
I'm surprised no one has said:
"just light load a .223". No fun in that. I believe the .221/.223 round will be very efficient.
I have many .223s including a tackdriving M12 BVSS.
If worse comes to worse, I'll just buy a new bbl from a custom bbl maker. For the Savage, they come in any twist, contour, material, etc. These are prethreaded and with the wrench and guages, it's a piece of cake.
BTW, Dave, the Axis and M110 use the same bbls and nuts....

ron