Festus, Thanks for the advice on H100V and Winchester 780 Supreme.
I believe that most of Hodgdon's extreme powders are made by ADI here in Oz, then rebadged by Hodgdon. I just checked the ADI website and there is no mention of a new powder with a burning rate between AR 2209 (H4350) and AR2213sc (H43831sc).
Winchester have made a habit of releasing a slow burning powder (780BR, 785, WMR, WXR) then ditching it about 3- 5 years later. So this time I may wait and see if the burning rate really suits my circumstances, as I still have ample supplies of 785, WMR, and WXR. Brian.