I have used the .416 Rem Mag. in a Remington 700 (400 gr. @ 2267 fps), and a stainless Winchester Mdl. 70 (400 gr. @ 2410 fps) on several Cape Buffalo, Hippo, Australian Water Buffalo, and 2 large Russian Brown Bears. Close friends have used it on bunches of Buffalo, Bison, Bears, and a couple of Elephant. The brass and dies are cheaper than the Rigby version, and recoil is less in a gun of equal weight, as the Rem. version uses less powder to achive 23-2400 fps. High pressures in the heat, and extreme velocity variations in the cold are absolutely not an issue to be concerned with. I use WW760, the same powder I use in my .375 H&H. The .416 Rem. Mag. shoots as flat as the Rigby with the same velocity, and a LOT flatter than the .458 Win. or Lott. A 500 gr. .458 has SIGNIFICANTLY more recoil than a 400 gr. 416 Rem. Mag., yet the .416 will easily kill anything. If you're using, say, 350 gr. bullets in a .458, then you're kidding yourself...you don't really have a .458. People want what they want, and that's fine with me, but I made my choice a long time ago. I'd pick the .416 Rem. Mag., without question.