Nitrox
I doubt that you can bring in a rimfire - I know that you can't in Botswana. I did use a 22LR on my first hunt - my PH's. We used it to pot shoot francoln. It was an old Brno with express, yes express, sights. We had a ball with it. The only reason that he could have it, they are illegal in Botswana, is that it was his grandfather's and thus already in the country when they were banned.
The francoln pie was excellent.
By the way - wouldn't a 22 rimfire double rifle be ton's of fun.
Terry