Aussielad, I just browsed thru Ackley's book(s) "Handbook for shooters and reloaders". Ackley didn't do this himself, in fact all of the .303 wildcats he discusses spring from Australia. Two basic variations listed, one being the simple necking down without further modification and the other being similar to Ackley's improved cartridges, or having blown out cases with sharp 45* shoulder and minimal taper. Fellow named Epps did most of the latter for what it's worth.
The simpler form was referenced in the following calibers:
.22-.303
6mm-303
.25-303
7mm-303
There was no discussion of a .308-303 but I don't see there would be any difficulty putting that together. For your information, the improved versions were primarily intended for the likes of Martini actions while the others were used in Lee Enfield rifles.
Hope that helps.
