Let me know how the Cerosafe chamber casting comes out. If it measures anywhere near where you want to be, yer good to go. If not, send the chamber casting along with about Five fired brass from that chamber to Reddington Die Specialists. They will want about $100 for a custom sizing die made to your exact chamber specs.
Then, you can find the nearest size brass and run it thru the custom die and trim it to exact length and enjoy all the benefits of a custom rifle.
I've done it a number of times on Mauser K98s of different wildcat calibers and chamberings, namely .25 Gibbs, 6.5mm Gibbs, .257 Durham Jet, 8mm-06 and others. Done right you end up with a die set that matches your gun so well that you hardly move any brass when you re-size.
Go for it.
DD-DLoS