The 22x357 Max, depending on reamer dimensions, will be identical to the .222 Rimmed, with a 0.2" shorter neck. 222 Rem data would be a good starting point, with an appropriate reduction in charge for deep-seated bullets. I'm doing something similar for a Martini Cadet, but based on longer 5.6x50R brass, necked to 0.257 (sort of a 256 Mag Long).