m77, your Kudu pic is just killing me to go back to SA for a hunt....;)
I have a remington 22-250 700 Varmint and it shoots scary well- with 40 grain ballistic tips, but with anything heavier it is very average at best. I would love to shoot some high BC bullets in it and my 223 AI, but the 1-12 and 1-14 twists they come in just don't allow it.
Go for the faster twist, 1-8/1-9 , even if it means getting a custom barrel if the Kimbers aren't available and shoot heavier, high BC .22 bullets and you'll always be glad you did. Thank Boxer later....
If you get a good barrel, heating shouldn't be any more problem than using a heavy varmint weight barrel if it is bedded properly, installed properly, and it is digesting loads it likes.
What kind of varmints are you after? I noticed a bunch of Dassies, and tons of birds when I was there. Wish I had a varmint rifle with me then....
Bob