Correct original loading for these is the original 7x57 Mauser cartridge with the 174-grain round-nosed bullet.
Original ammo was German manufacture, headstamped DM K and a date (eg: 18 99).
If going through original Boer ammo, check for cartridges with a SHORT NECK: these are 7x54 Mauser cartridges, very rare, go for piles of money.
This is a nice-shooting cartridge with the 140-grain bullet and is capable of accuracy that would absolutely frighten your socks off.