The 307 Win is a semi-rimed cartridge with very little for the extractor to grab, but has gotten my attention for making a 243 rimmed cartridge for a double rifle! All that would be is to run the 307 case in a 7mm neck die, and then a 243 die to form the brass.
However this would certainly go over 50K in pressure. I still wish I had my 30-30 double back!