Home Forums Hunting & Shooting Express Rifles and Big Bores Only The great 458 Winchester. Everyone should own one at least once

Interesting tests for "TBI" (ThermoBallisticIndependence) of some powders in the .223 RM
with heavy bullets for caliber (64gr and 75gr)
by "Mr. T " (T_the_Tinkerer, of Hammer Time Forums):

https://hammerbullets.com/hammertime/threads/temperature-test-2.798/

Any propellant good in the .223 RM is good in the .458 WM.
Many excellent new ball powders have been developed recently.
The .458 WM just keeps getting better and better.

AA-2230 and AA-2460 post-2016 have mediocre TBI compared to some,
but they are still quite good compared to how ball powders used to be in the past,
and a lot better than the old IMR stick powders.
Still top performers in the .458 WM, just be aware of the "not bad TBI" and make allowance for heat.







Get a load of the "paradoxical" AR-Comp, with velocity increasing in extreme cold,
leveling off in the midrange temps and increasing very little in extreme heat.

Ditto Benchmark, the "Extreme" stick powder by Hodgdon, but even better TBI,
almost a flat and level line for velocity from -8*F to +162*F.

X-Terminator used to be identical to AA-2230, some say, still pretty close, and has better TBI.

IMR-3031 was the old standard for .458 WM and 500-gr bullets, easy to do 2150 fps in a 24" barrel, even back in the dark ages.
Hodgdon's Benchmark Extreme may be substituted grain for grain in the .458 WM to replace the IMR-3031.
This should be done by no later than yesterday.