Load Specifications
Load data in caliber .458 SOCOM with .458 | 405gr | Rim Rock RNFP Top Shelf bullet and 7 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2207, Vihtavuori N120 and ReloadSwiss RS 14.
Important Notice: DO NOT go below Minimum Charge or above Maximum Charge. Since we have no control over the equipment and components used, any responsibility and liability for the results achieved is rejected.
Only powders/loads that match the current filter criteria are displayed: max pressure of a load ≤ 90% of max. standardized pressure, fill rate ≥ 80% and propellant combustion ≥ 95%. Use the sliders above the tables to adjust these thresholds.
Charge: Powder weight in grains. Start with the minimum load and work up carefully.
FR (Fill Rate): Case fill as a percentage. Values above 100% mean compressed loads.
MaxP / %: Maximum chamber pressure in bar and as a percentage of the standardized maximum for this caliber.
V(0): Muzzle velocity in feet per second (fps) at the standardized barrel length.
z (Powder Burn): Estimated propellant combustion percentage at bullet exit.
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Max Load - Barrel Length: 16"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AR 2207 | <<locked>> | 90% | 30,342 psi | 87% | 1631 fps | 97.2% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 27,876 psi | 80% | 1056 fps | 100% |
| IMR 4227 | <<locked>> | 82% | 31,357 psi | 90% | 1568 fps | 96% |
| Lovex S053 | <<locked>> | 82% | 30,197 psi | 86% | 1558 fps | 98.8% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 27,079 psi | 77% | 1083 fps | 100% |
| SNPE Vectan BA6 1/2 | <<locked>> | 84% | 30,313 psi | 87% | 1493 fps | 100% |
| Vihtavuori N120 | <<locked>> | 90% | 30,864 psi | 88% | 1617 fps | 98.4% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 16"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AR 2207 | 34.9 gr | 84% | 25,106 psi | 72% | 1532 fps | 95% |
| Hodgdon TrailBoss | <<locked>> | 80% | 20,059 psi | 57% | 942 fps | 100% |
| IMR 4227 | <<locked>> | 80% | 29,457 psi | 84% | 1535 fps | 95.3% |
| Lovex S053 | <<locked>> | 80% | 28,413 psi | 81% | 1526 fps | 98.3% |
| ReloadSwiss RS 14 | 12.2 gr | 80% | 19,348 psi | 55% | 961 fps | 100% |
| SNPE Vectan BA6 1/2 | <<locked>> | 80% | 27,137 psi | 78% | 1444 fps | 100% |
| Vihtavuori N120 | 34.1 gr | 82% | 24,120 psi | 69% | 1490 fps | 95.8% |
Recommended = one of the top powders for this cartridge and bullet combination.
ᴾ possible press load - work up slowly to this load while watching for signs of excessive pressure.
This overview compares 14 powders for .458 SOCOM loaded with the .458 | 405gr | Rim Rock RNFP Top Shelf. Alliant Reloder-10x delivers the highest muzzle velocity at 1,657 fps; across all powders the maximum-charge window runs from 1,056 fps to 1,657 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 14 of the 14 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (241 MPa), the top charges use 77–90 %, leaving at least 10 % headroom. Hodgdon TrailBoss, ReloadSwiss RS 14 reach 100 % fill or more at maximum charge, so these are compressed loads: they need a long drop tube to seat cleanly and react sensitively to the case capacity of your own brass lot. ADI AR 2207, Vihtavuori N120, ReloadSwiss RS 14 rank at the top here: for .458 SOCOM with the .458 | 405gr | Rim Rock RNFP Top Shelf they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Accurate 1680, Alliant Reloder-10x, Alliant Reloder-7 burn incompletely and react more sensitively to barrel length and temperature. Hodgdon TrailBoss, ReloadSwiss RS 14 stay subsonic at start load. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.