I agree a good 30-06 in 180 grain bullets will take any plains game in Africa. Ammo is widely available and fairly cheap compared to other calibers....and there are other grain combinations the 30-06 can shoot.
Seeing how your more of an archery guy, you are probably not wanting to spend big dollars on the rifle. IMO, the best rifle for the money out there is the Tikka T3 Lite series. Very accurate, very reliable and lightweight for carrying. It is not a thing of beauty, but that's why it's less expensive. Put a Leupold VX3 on 3.5-10 top and you'll have a very reliable and accurate rifle for about $1000. If you want to spend a bit less, then perhaps a Nikon scope.
The only back up gun I have ever wanted while bowhunting was a shotgun. I have been close to a bunch of Mambas, adders, etc. In the blind, in the tree and while tracking. Gawd I really dont like snakes.
i have purchased the tikka t-3 light in 300wsm. it is a great calibre. i also own 30-06 amd 308 and several others. the 300wsm has a little more jam and thats why i would recommend it. i hunt moose in canada and plains game in africa and it performs well.
I'll throw in another vote for the Tikka T3. I have one in .270 topped with a zeiss and have taken whitetails, mulies, moose and elk with it with nothing going more than 10 yards. It's a tough little rifle for a good price and don't be fooled by people saying the plastic clip is "no good". Saskatchewan gets very cold and up to +40 in the summer and I've never had a problem with the clip. I also have a Sako in .300 win mag and would use the T3 over it anyday(not because of recoil).
If this is a carry a lot, shoot rarely, backup on your bow hunts, I would suggest a Remington model 7 in 308. It is light, compact and is pretty much as good as a 30-06 (It pains me to say that because I love the 30-06 for plains game). If you want to limit your cost go for a savage, I don't have personal experience with them but many people claim that they are the most accurate out of the box rifle you can get, and they are cheap. If you want a little less thump, go for a 7mm 08. While they are a little small for the larger plains game, just about everything has been taken with one.
I would stick to the 30-06 for the following reasons:
1. Variety of loads - if you reload you can load anything from a 130 grain for varmint hunting up to 220 grain for bigger animals in bushveld conditions.
2. Availability of factory ammuniton- you could walk into any firearm store in South Africa and buy factory ammo off the shelf.
3. The 7mm-08 is not popoular in South Africa and factory loaded ammo is not easy to come by. ( .270 and 25-06 is more readily available ).
I would go 308 or 30-06. But given the choice 30-06. In terms of which rifle?? Well seeing as its going to be used rarely anything should do. I would also back a T3 as its almost the same as a Sako (same factory (many of the same components too)).
Played rookie league for the Yankees in Paintsville after winning the College World Series at Fullerton State, in1979. All I could think about was the movie “Deliverance”- lived up in a hollow with some other players. Refused to go on a moonshine run because it was a dry county-no way. Met some of the nicest people on the planet there! Van Lear the home of Loretta Lynn was highlight of summer LOL.
Mule deer and Colorado elk seasons almost done! Hunters driving farm roads, looking for racks, their PH driving them along, I ask that you not pull into my drive. The buck behind me, on the boundary line of the GMU somehow knows. The hunter laughs, I would invite you in to see my Searcy rifles but social distancing prevails, darkness arrives and the buck slides away into secret tree grove...