I can only speak from experience with the .340 wby but they prity much identical in power, if you can handle the rifle and shoot it well its great for everything. I would think nothing of hunting cape buffalo with one. If it was legal of course.
Phil , the 338 RUM is a mean rifle, and you would certainly be able to take all of the plains game with it. Most countries , as mentioned, has a minimum of the .375 for DG. If you can handle it, without it dislodging the fillings in your teeth ,it should not let you down. But a calibre in .308 or 30-06 range will do all you need it too on plains game. Some people take recoil with ease, others not.
But i'm with you, you can never have enough rifles.
It will depend on your ability to hit what you are aiming and shooting at with your new rifle. Sometimes you need to go with old reliable that you have great confidence in and know that you can make the shot. Not all shots are going to be standing broadside and 50 yards away. Sometimes you will be lucky to get a 300 yard shot at a real trophy that you made a move on for over 2 miles of tracking. You just do not want to muff the shot…
Wounded game is not the way to go. You’re PH and trackers will not be happy with you it they have to continually follow up wounded game animals.
If you have the ability to consistently make killing shots out to 300 yards then that would be the rifle for you to take.
A little test for you to try: See if you can hit a golf ball at the rifle range from 50 to 100 yards with your new rifle. Shooting from a bench and then off hand. If you are not able to do this then leave your new gun at home.
Second items are having great ammunition and reliable bullets, this will help with your process.
As many have already mentioned this caliber is more than adequate for any antelope on the African continent.
It is really not needed, with the eland the .338 and similar calibers are highly recommended.
I have a .338 win mag. but have only taken it to Africa on one occassion. I have found my 30-06 comfortable, I am confident with it and it has taken several species sucessfully. The key is being comfortable and confident in your rifle. Remember, if you wound it and don't find it, you still pay for it.
I've had a little experience with this rifle / cartridge combination. I've worked with a friend to develop loads for his 338 RUM. After testing a number bullet/powder/seating combinations, good accuracy was only obtained with loads that were well below "maximum".
As others have said, it's also a kicking SOB. The recoil is pretty "sharp". If recoil is not a factor for you, don't worry about it. If you tend to flinch, shoot something you are comfortable with.
I gotta admit, it's a powerful firearm, but power isn't everything.
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...