I have used the 7x57 for many years here in Pennsylvania since I was 14 using 175 grains cause the were cheap and I was broke. That big, long, round nose never failed me. It wasn't sexy, it just put 2 holes in every animal if I did my job. That's when I discovered 2 holes are better than one. Other guys in camp mostly WW II Vets and us kids had been bitten by the magnumitis bug, more speed, more power, the trade being less accuracy. I too was bitten for a while using a 7mm Rem Mag, nice gun went back to the little seven. I was 17 and a skinny kid at the time. My buddy knew the key to success was excess, to do me one better bought an Interarms Mark X in 300 Win Mag
He missed the biggest 8 point he had ever seen up to that time and he would never admit it but it was him being afraid of his rifle or more to the point his choice in calibers.
I went on my first Safari in 2012 I took my 76 Dakota 275 Rigby and a 338 Federal Custom John Gallagher rifle based on a Remington model 7 skeltonized, shot 9 animals with 11 shots including the insurance on a Cape Kudu. My opinion is if you like the 7x57, try a .338 federal I can't think of a better African cartridge for game up to 600/700 pounds, performance way beyond that of cartridge capacity, in a nicely, balanced quick handling fly rod of a rifle.
The Federal duplicates everything that the old classics .333 Jeffrey .318 Westley Richards did and also the 338/06 and the South African .338 Sabi
If you want to see something neat go on Federal's website and compare the 338 Federal to the 300 Win Mag and the 338 Win Mag.
By the way on my trip to South Africa
I used
185 TSX in the 338
160 TSX in the 275
We never recovered a bullet