I shot the old Spanish 7mm with cast bullets to good effect, but in a Remington 'Roller'. Neck dia. is larger and the headspace a bit short on commercial 7x57, but a handloader can make it all work. Ive never read anything about this cartridge difference in Spanish Mausers so maybe it was something from the Poncho Villa revolution?
The 7x57 is an under-rated cartridge here in the USA, though we do have the 270 and various 280s that are thought highly of. I expect 99% of game taken with those would have been bagged with the 7x 57 too.
As to my current project old Mauser, as far as I can decipher its a 1918 DWM, Berlin made Gew98/Kar98 pre WWII Weimar rework in 8X57 that the stock was Bubba-Sportered years ago. It is not going to get any rebuild, just fit it all up to wring any inherent accuracy left out of it and see what the old warhorse will do. Those mil sights are only good for 100yd. with my eyes, and 50 is probably more like it, but a whitetail at 100 has a generous heart/lung area so I hope I can get a max 4" groupability.
BTW, Im not up on Mausers at all, so this has been my first 'research' project on one. There is a plethora of info online, but hours, if not days to get through it on variations, numbers, codes, etc.
Wish I had picked up one of those South African/Boer War Mausers back when they were affordable (the pre 98 variations), just something about that history intrigues me.