I thought I'd seen 1800-2100 on the woodleigh site.

Went back and copied this:

30 458 Mag .458" 400gr PP 1900-2250
You might want to double check the 2500 number.

Still, for your interest the range of impact velocity seems it might be narrow.
I'd phone the guys at woodleigh.

I'd chosen the 350gr Barnes spritzer X-bullet years ago for many reasons, including the wide range of effective impact velocities.
It might help you to look at it, perhaps to test it.

Cheers
Tinker