Here is the story. I do not now nor have I ever owned a 340 Weatherby in fact I would not buy a Weatherby rifle under any circumstances, but that is another story. I do like some of his caliber the 300 and 340 are two of his best efforts.
Around 1980 I wanted a flat shooting long range caliber suitable for the largest non dangerous game. Like a lot of Keith’s readers I was fascinated by the 338/378 Keith. I also believed then and know now from personal experience that heavy properly constructed bullet (for the species hunted) is better than a lighter bullet. I believe in shooting thru an animal (two holes are better than one) and having adequate penetration for a south end shot on wounded game. I am not a fanatic about super high velocity but it takes a combination of velocity and high bullet co-efficiency to flatten out trajectory.
I corresponded with Elmer on this subject and on a side note if I can find the letters I will scan them in to this forum. Elmer felt the 338 378 was a very expensive proposition both from a rifle and a case forming stand point. It took a magnum Mauser, Champlin or Weatherby size action for the build and you had to modify 378 Wby cases. Thirty years ago that was about all that was available. I decided to approach it differently and was determined to get 3,000 fps with a 250 grain bullet. In Elmer’s opinion this was the best long range combination. Look at high the BC on a Sierra 250 grain boat tail although I went on to use Nosler Partitions as my standard bullet.
I went on to design a case for a single shot rifle (got around the action length problem) sort of a poor mans 338/378 Keith. Also keep in mind the Keith cartridge is not simply a necked down 378 but the shoulder is pushed back and the case capacity was more in balance with the bore. There are three of my caliber rifles in use today by friends who borrowed the chamber reamer.
Anyway I am sorry I am going the long way about answering your question. If you look at ballistic tables in say a Sierra manual and take a 250 grain .338 @ 3,000 fps compare it with a 270 grain 375 @ what ever velocity it is capable of short of a 378 you will not hit 3,000 fps you will see the .338 is flatter shooting and has more retained energy. I spent a lot of time pouring over these tables before making a decision. By the way I have chronographed my cartridge with 250 grain bullets @ over 3200 fps but was uncertain as to what bullets might do at close ranges so I backed it down to 3,000.
The reason I suggested a 340 as Elmer did to me is because it is less expensive and fairly close to the wildcats in performance.
After developing my cartridge I had the opportunity to use it on culls shooting literally hundreds of animals with it. I also shot a number of animals out to 500 yards which is what I consider my maximum distance given a steady rest. It had amazing knock down power at that range even on poorly placed hits.
In Africa you are not normally shooting at long ranges the exceptions being desert species and some of the swamp areas where say 350 yard shots are not uncommon. I have had a number of people use a 300 mag in fact my bean field rifle is a 300 Jarrett. These are fine calibers but somewhat marginal on large kudu or an eland which can exceed 2000 lbs. Truth is a good argument could be made for a 300 and a 416. The 416 with a scope could be used for the largest antelope.
But at the end of the day the single most important thing is bullet placement and bullet construction.
Most of the buffalo and elephant I have shot has been with a 475 # 2 Jeffrey double which was a hammer although technically it was not a stopping rifle. In truth there are many combinations of calibers that can and have worked and at the end of the day it is personal preference.
