Why not just buy new .222 Rimmed brass? Midway, Huntingtons and Grafs list it as "in stock", and no doubt there are others too.
$36.49 for a box of 20 from Midway. $39 for the last bag of 100 new Remington 357 Maximum I bought.
Yeah, that is a fair sort of reason. Here the very same .222 Rimmed brass is about $71 US per hundred. Clearly someone's charging a good deal to get it from here to there, or perhaps bought it when our dollar was higher against yours.
There's still the stuffing around needed to turn the .357 Max into what you want, but even that would probably favour using the stuff you have given the price difference.
