Ironman, Glad you have dug out of the post safari pit enough to post again. You are a legend. Cue Tennessee Ernie Ford singing "Big Jerry" but with lyrics about safari ...
Here is something funny. The .458 B&M+ with 16.875" barrel gave 2367 fps MV with the 404-gr Shock Hammer and a charge of 80.0 grains of AA-2230. That is in a Pac-Nor 1:10" twist stainless "Super Match." I SWAG that increasing the length to 24" would add 150 fps. Velocity would become 2517 fps. Just 1 fps below your fps for the Safari Load.
The new Pac-Nor will be installed on a .458 WM+ Mauser, 24". .458 B&M+ is same as .458 WM+, only shorter. Of course, I will have to compare the AA-2460 max load to the AA-2230 standard load with the 404-gr Shock Hammer as well as the 400-gr CEB #13 FN.
LOL, ironman these days is a quickly fading memory, i may have been a pretty good dog 30 years ago, but holy crap, "Papa Time" is a damn thief!
This is all very good stuff, you keep fooling with those 16 barreled rifles, you'll have to book a hunt in dot head land for a giant Gaur in the magic carpet land thickets ; ]