I'll chip in my $.02 since I have both feet in both camps.

The ideal for a DR is a low pressure rimmed cartridge. There is simply less to go wrong and less reason for it to go wrong.

Don't pass up an opportunity to own a nice rifle that isn't ideal simply because it is chambered for a higher pressure rimless cartridge though, even if it is going to see use against DG.

I bought my rifle which is in 458wm for a song because it was heavily discounted because of the chambering. I vetted it thouroughly before using it for DG. JJ inspected and shot it and sugested I try to make it fail. I fired more than 200 rounds without cleaning the chambers or the ejectors in an effort to get the rifle to fail. It worked flawlessly every time. I have about 500 rounds through it and performance has been flawless.

The dust in Africa is fine and plentiful, actually endless. It is something to be aware of and to combat no matter what type of rifle you are using. In fact, dust was more of an issue with my bolt rifle than my double. I found that it is an issue when your rifles are in the back of the truck, traveling. It is easy to combat by using a good softcase and also a sleeve. When you are on tracks the dust isn't much, if any, of an issue. A good dust cleaning at the end of the day for whatever rifles you have had in the truck, bolt or double, is an easy and wise dose of prevention.

A good quality rifle in a higher pressure belted rimless cartridge just isn't the accident waiting to happen that some beleive it is. This may not apply to lesser quality rifles and I would thouroughly vett any rifle going on an extensive hunt, particularly a DG hunt and particularly rimless cartridge DR's. Then I would confidently takle any game on earth.

JPK