Most accounts of this cartridge are essentially parroting of the above noted text.

COTW doesn't account for the numerous .318" 8x60 magnum rifles that are out there, if one were only to use that book as a reference they'd surely end up getting confused.
Also, using the militaria-collector standard of 'reduced loads only for the .318" rifles...' will leave many owners of .318" full nitro 8x60 rifles short-run when it comes to getting their nice, early 20th century sporting Nitro rifles up to their potential.

Furthermore, Fraserdouble --
This rifle you're considering might not like Varget.
I've been working with 2015BR in cartridges from the .458 winchester down to the 25-20.
It's been a marvelous full-case powder, very consistent in velocities, hasn't shown up to be temperature sensitive either. I don't know what the load would be for this powder in the 8x60 as I haven't tried it yet in my 8x60 rifles, one of which is a SxS BLE and has shown to be very sensitive to different powder choices at similar velocities.
Get your chronograph, your dies, and your powder scale and get to the shooting bench with that Mauser!

Some of what this all boils down to is that if you're looking at an 8x60 sporting rifle from the early-mid 20th century, it's important that you take everything into account.
This is one of those cartridges that will test the crowd for sure.

It's a cartridge that's truly one for the Handloader, and one's experience and care from the reloading bench to the shooting bench will greatly reward him.

--Tinker