Well, it seems AA-1680 might be about as perfect as AA-5744 for use in the .458 WinMag with 250-ish grain bullets at around 3000 fps MV from a 24" barrel.

Here is the donor rifle for for a 1:10" twist .458 WinMag capable of handling the 575-gr CEB Lazer hunting bullet.

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Maybe CFE-223 would be a good powder for that one.
Sir Jerry has a doozy .400 Whelen load with that powder pushing 400-grainers to well over 2200 fps in a 23" barrel,
at normal temperatures stateside
and he had no trouble at ambient temp of 41*C, baking in Africa.
That is 105.8 degrees F.
That is brain-damage fever.
Or compressed H4895 or non-compressed AA-2460 would get the 575-grainers past 2000 fps.

Barrel: My previous 1:10" twist, .458"-grooved (slugged by me), 8-grooved, No. 4 Sporter stainless "Super Match" barrel from Pac-Nor
was cut to 19.75" on a .458 B&M, which has been re-throated with a .458 WinMag reamer.
It is now a ".458 B&M+W" which is what I am calling it this week instead of a ".458 BMW."
That will do lesser velocity trial loads with the 575-gr Lazer from CEB,
when I load it like a shell-holder action (M70 short action for WSM).

Looks like I need another Pac-Nor like Sir Jerry suggested.
This time a No. 6 Sporter "Super Match" to finish up at 28" length.
Fitted with Creedmoor iron sights and a Picatinny rail it might be about 10 pounds.
Lengthening the barrel from 24" to 28" only adds 0.33 pound according to the Pac-Nor barrel weight calculator.
Don't gain much after 28" of barrel,
start losing velocity about 30" barrel length with these new-fangled smokeless powders.

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The .458 WinMag Creedmoor rifle is third in line at the Hilltop Gun Shop & Spa for Wayward Rifles.
1. 500 Jeffery Match CZ 550 Magnum for duplicating .50-140-3.5" BPCR loads with 1:20" twist McGowen stainless.
2. 400 Whelen Ruger M77 Hawkeye awaiting barrel hardware add-ons.
3. .458 WM Creedmoor Ruger No. 1.


Ron aka "Rip" for Riflecrank Internationale Permanente
NRA Life Benefactor and Beneficiary
.458 Winchester Magnum, Magnanimous in Victory
THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.