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Comments to Sir Michael at MIB:

Michael458,
Plumb prolific of you.
Nice additions to the spread sheet for the 20″-barrel data for 2022.
It’s all good, the more powders the merrier.
Thank you very much.

What powder do I like best with the 404-gr Shock Hammer ?
AA-2230 of course.
I am going to take your loads with the old AA-2230 with a grain of saltpeter, however.

Why did Western Powders have to reformulate the AA-2230 and AA-2460 in 2016 anyway ?
Must have been a problem with the old formulae.
The change was said to have made them more stable in the thermoballistic way, less temperature sensitive.
That got my attention.

I never used any AA-2230 until 2017 when I had my .458 WinMag resurrection.
AA-2230 was the most commonly recommended powder by many when I resumed reloading for the .458 WM,
and I have not been disappointed.

I think AA-2230 and AA-2460 are the same chemical composition, my SWAG:
The tiny balls of AA-2230 are about a 50:50 mixture of perfect spheres and flattened ones (oblate spheroids).
All of the AA-2460 balls seem to be perfect spheres.
The mixture of flattened granules and spherical ones allows the AA-2230 a more compact loading for same weight of powder,
and there is a greater surface area on the flattened granules for quicker ignition.
So AA-2230 is a slightly faster powder requiring no compression when same weight of AA-2460 requires some compression.
Not much difference between them.
Flatten half the granules in AA-2460 and you have AA-2230.
I prefer AA-2460 for 450-500-grainers,
and AA-2230 for 400-grainers.

404-gr Shock Hammer
WW-Super brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
39*F
25″ Shilen barrel, .458 WinMag:
AA-2230 81.0 grains >>> 2507 fps (5-yard), 2517 fps MV (estimated 20″ velocity = 2427 fps MV)

404-gr Shock Hammer
NORMA brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
40*F
25″ Shilen barrel, .458 WinMag:
AA-2230 84.0 grains >>> 2535 fps (5-yard), 2545 fps MV (estimated 20″ velocity = 2455 fps MV)

Here are faster-burner powders that might get pressures higher but seem trouble-free in same rifle as used above:

404-gr Shock Hammer
WW-Super brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
86*F
25″ Shilen barrel, .458 WinMag:
H4198 72.0 grains >>> 2504 fps (5-yard), 2514 fps MV (estimated 20″ velocity = 2424 fps MV)

404-gr Shock Hammer
WW-Super brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
86*F
25″ Shilen barrel, .458 WinMag:
H322 78.0 grains >>> 2500 fps (5-yard), 2510 fps MV (estimated 20″ velocity = 2420 fps MV)

SHORTER COL FOR HIGHER MV:

NORMA brass
80.0 grains AA-2230 with 404-gr Shock Hammer, 40*F, 25″ Shilen barrel
3.380″ COL >>> 2488 fps MV
3.480″ COL >>> 2425 fps MV … lost 63 fps by loading 0.100″ longer COL

MORE POWDER MAKES UP FOR LONGER COL MV LOSS:

Same day, same rifle, same 40*F temp, same 3.480″ load with 4 grains more powder
84.0 grains AA-2230 >>> 2545 fps MV … gained 120 fps MV
(82.0 grains in 3.480″ COL is about equal to 80.0 grains in 3.380″ COL)

It is about a 10-hour drive to haul new-version AA-2230 to the MIB laboratory.
I am thinking about it. Owe you for that steak dinner at DSC 2013.