I have culled a lot of Springbok, Blesbok with the 6x45 and the 75gr. Barnes X bullet and it works fine...I have shot a number of mule deer and pronghorn antelope with it, but I had to modify my hunting methods to meet the capabilities of the gun, I expect the same applies to the .243...It is popular in Africa as is the 6x45...

But I will have to agree with Shakari on this one, I personally wouldn't recommend either 6mm for the American hunting Africa, and would strongly suggest a 30-06 and up, the 300s and 338s being the best for an all around plainsgame rifles,...This does not mean that anyone who wishes to shoot a lesser caliber can not, thats up to them, not me.....I don't care what anyone uses if they are confident and happy with it.....