I always start with the minimum charge and work up, yes you might not get the velocity you're wanting but accuracy is generally first and foremost especially with a long reaching cartridge like the 270 wsm. I just finished working up a load for a 257 Weatherby, it preferred the smaller charges when it came to accuracy and in the end I had the rifle shooting under 1" groups at 100 which translated into 3"-4" groups at 400. I'll take a loss in velocity if I can get rifle to shoot like that.