I have a friend headed to Africa for the first time. He has time to purchase a rifle and get comfortable if necessary. He has a .270 that shoots well (Tikka). He is not a handloader. Game would be typical plains game including Kudu, Waterbuck, Zebra, Gemsbok, and down to Impala. No Eland or larger. I've been once, used a 338 Federal shooting TTSXs and it worked fabulously. What cartridge would those of you with significant experience recommend? He will stick to a premium bullets per the PH's guidance. (Bonded, A-Frame, Mono, etc.). I believe all of these cartridges listed below would work, but I'm tossing this out there to gain any unique insights I haven't thought of.
Stay with his .270 using a heavy, premium bullet? or...
308 Win
7RM
280
30-06
300WM
If I were to go back to Africa again, for the species listed, I would once again be taking my .300 Weatherby, this time with 165 gr. Barnes TTSX bullets. Second choice would be my .30-06, again with the 165 gr. TTSX. Either will work wonderfully well, as well as any other .300 mag. cartridge. Check out some of JJ Hack's past posts regarding caliber and bullet choices for African plains game, he knows whereof he speaks.
