I've never done anything with it, nor seen any wildcats in person.
But, I have seen references to it being used for 6mm cartridges (like ".243 Rimmed") and "short" variations of some of the JDJ wildcats that are based on .444 Marlin.
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T. O'Heir,
Winchester still produces .307 Win brass and loaded ammo (180 gr PP @ 2500 fps) about once a year - minus a few years during the recent '8-year-shortage'.
They just ran some last June or July, I believe it was. In October or November, I picked up 6 boxes of loaded ammo for less than I could buy the equivalent number of cases in 50-count bags of brass; and the retailer still had about 600 rounds in stock at that point.
Even if .307 Win brass did completely go the way of the Dodo, it's easy enough to form from .444 Marlin, which is easily obtained and growing in popularity. (Recently added to the catalog by Starline, even.)