There is also a 400 Whelen. It's .411" bullets are considered max for an 06 case. Most of my o6 based Ackleys have .465" shoulders, so maybe a .416" bullet might work. Pretty much splitting hairs.How much shoulder is needed for a positive headspace.
From American Rifleman 9-1-23

And a better & newer version r/clicked from the internet somewhere.










