Well to be quite honest, I have not found a need for anything bigger than the 265gr wide flat nose gas check from Cast Performance,
http://www.castperformance.com/Detail.bok?no=18It will shoot lengthwise through a 200# feral hog with only the starting load they recommended. This is fine with me as it shoot very nicely from my Ragin Bull. Groups at 25yds are around 2" or less depending on how well I am on that day.
Give them a ring and ask about their data, they are a great bunch of folks. There is a light load for this bullet listed using Trail Boss on the Hodgdon site, but the one I am using is with their recommended start load of 296.