Mmmm, two pre-64 M-70s, just plain greedy!

9ThreeXFifty7:
I neck-up .338 cases, rather than neck down .458s. Thin necks last longer between annealing than thick necks in my experience. My Peter Davern Custom dies have a long tapered neck-expander which pops them up in one pass, I've never lost a single case during forming. After necking-up, they are ready to shoot, no fire-forming loads necessary.

Modifying a military Mauser is pretty easy, just open-up the bolt-face and grind a bit out under the feed-rails, polish, and you're done. I think Vic might have modified the follower slightly for the fatter case, too. ...and bevel the follower to close the bolt on an empty mag, which goes without saying.

Another pic for you, 9ThreeXFifty7. My eldest daughter with her last Taylor buff, another one shot kill: