I've researched this heavily and I can tell you that you usually bring two guns since you always need a backup. 2 guns is the max you can bring to most of Africa and they must be different calibers.
My opinion, .338 is the worst choice because it's overkill for some and not big enough for others.
The classic rifle for accuracy and light recoil on plains game is 7x57. The classic magnum for plains game (and legal minimum for giraffe and eland in some countries) is 300 H&H.
The minimum caliber for dangerous game is 9.3x62 or .375 H&H. If you could bring only one gun and you want to shoot anything, it's 375 H&H.
I'm taking a 7x57 and 300 H&H as I don't intend to hunt big 5. Those will do all the other game effectively.
A 300 win mag is also a good choice for all but big-5. Legally speaking .300 can take big cats in many places but most suggest .375 for best versatility.
