for me doing anything like this I find that a few steps work better than making the jump in one move, I would suggest going up to 6.5, annealing then try to go that rest of the way, if you have problems with split necks then don't hesitate to go to 277 or 7mm before going to 308. I have taken 25 wssm and made 358 bfg from that so going to 25 cal to 358 is a bunch more that what you are trying to do. good luck