Also let me add that a couble of months ago I was at the range and met a guy that was getting ready for Africa. He had been several times before, saw the pictures, and he has several double rifles, including some big name British and some new made German ones. The rifle he had at the range that day was a Heym in 458 Win Mag, with a scope. He said that this was his favorite double to hunt with. It shot real well and it handled good too. He was shooting reloads with X bullets. He stated he had never had any extraction problems. I spoke with him after his trip and once again he had no problems with the rimless double.
Chapuis also makes a 416 Rigby double rifle.