If a rifle won't feed or chamber when dusty, there is something really wrong with the rifle...
People take all sorts of cartridges to Africa, few of them shaped like an H&H...They seem to work okay, no reason why the NEW KING won't work, too.
Well the thing is most of the guns going over there, after anything big and dangerous, are .375 H&H's. My PH said that the number of hunters showing up with a .375 H&H outnumbers all other calibers of guns combined that he's had show up in camp for dangerous game. So while many are shaped differently, doesn't mean much when most of them are H&H's! I talked to people here from CGN who had chambering issues with modern cartridges right before I left, not uncommon. There's something to be said for your brass not contacting the chamber walls until the very last minute when camming into battery on bolt closure, due to healthy taper, and even more to be said for it being broken completely out of contact with the chamber walls on extraction the second you lift the bolt handle.

Like I said, I'm no "ardent" opponent of the Ruger, I think it's a fine cartridge that was designed for more little-bit-of-everything shooting, especially North American shooting. When it comes to Africa mind you, the H&H is the hands down winner, better in high heat there's no argument (lower pressure, and tapered), better in fine dust again no argument (slicker feeding, taper handles dust better than straight bottleneck), and likely most critically; you can get ammo anywhere on earth. Would I take a .375 Ruger to Africa and feel confident? Hell yes, just like I would with a .404 Jeffery, but I had the choice, and chose the H&H. Happy with my choice, the Ruger fellas have good reasons to be happy with theirs too, for you can own a few .375 Rugers, one short blued/wood, one long, and one stainless/synthetic, for the price of one decent .375 H&H. For a "get-to-it" hunter, the Ruger wins, it's a sensible choice. When everything has to be perfect though, I choose the H&H. Personal preferences all 'round...