When I owned my .416 Rigby I loved it, but I hated the cost of that Norma brass. For those of us on a tighter budget who want a hotrod .458 I would choose the .375 RUM case. A .458/375 Ultra is very similar to the .460 G&A which was developed back in the early '70's. Brass is affordable and available, and 500 gr bullets can be pushed at 2400 fps without undue pressure. I think with the Ultra family of catridges on the horizon, Remington missed the boat by not bringing their .416 and a .458 out on the Ultra platform.