Alright, concensus is that a .005" taper and a .035" shoulder is "enough."
So, despite the din from the nay-sayers, I'm reclaiming this wildcat as a real possibility. I still may do the .475" version, but the .510" holds a strong allure.
It's a Rigby case, blown-out and shortened, set up for a 3.1" COL, ala M70's, k98's Yugo's, MRC1999's, etc.
Base is nominal .589" tapering to .570", 35* shoulder, .40" neck measuring .5350"-.5340" bottom to top, case 2.4" long, .70" nose, 1.1" base of neck to 3.1" COL.
Should hold ~133-4g water to top of case. 500 Jeffery is about 160-5g water.
Powley suggests a 600g going 2200fps at about 41k CUP. But will it feed?
Things to make you go "hmmmm"....

-and if anyone has Quickload, and a few secs, please check out a 600g 1.268" bullet loaded to 53.6kpsi from a 24"bbl.
Assuming a M70 can handle the WSM at 62kpsi, the boltthrust should be similar. Something akin to 47.5k CUP?