Load Specifications
Load data in caliber .45-70 Govt. with .458 | 405gr | Remington SP bullet and 6 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant AR-Comp, ReloadSwiss RS 14 and Hodgdon TrailBoss.
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: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Alliant AR-Comp | <<locked>> | 92% | 27,267 psi | 85% | 1762 fps | 96.6% |
| Alliant Reloder-10x | <<locked>> | 86% | 28,123 psi | 88% | 1752 fps | 96.2% |
| Hodgdon TrailBoss | <<locked>> | 96% | 28,355 psi | 89% | 1145 fps | 100% |
| IMR 4198 | <<locked>> | 82% | 28,108 psi | 88% | 1693 fps | 96.7% |
| Norma 200 | <<locked>> | 82% | 27,992 psi | 88% | 1742 fps | 97% |
| ReloadSwiss RS 14 | <<locked>> | 98% | 28,863 psi | 90% | 1188 fps | 100% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Alliant AR-Comp | 44.7 gr | 90% | 25,686 psi | 81% | 1726 fps | 95.8% |
| Alliant Reloder-10x | <<locked>> | 84% | 26,382 psi | 83% | 1716 fps | 95.4% |
| Hodgdon TrailBoss | 13.8 gr | 80% | 21,959 psi | 69% | 1043 fps | 100% |
| IMR 4198 | <<locked>> | 80% | 26,455 psi | 83% | 1657 fps | 95.9% |
| Norma 200 | <<locked>> | 80% | 26,324 psi | 83% | 1706 fps | 96.3% |
| ReloadSwiss RS 14 | 14.1 gr | 80% | 21,712 psi | 68% | 1070 fps | 100% |
Recommended = one of the top powders for this cartridge and bullet combination.
This overview compares 6 powders for .45-70 Govt. loaded with the .458 | 405gr | Remington SP. Alliant AR-Comp delivers the highest muzzle velocity at 1,762 fps; across all powders the maximum-charge window runs from 1,145 fps to 1,762 fps. ReloadSwiss RS 14 gives the best case fill at 98 %, and 6 of the 6 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (220 MPa), the top charges use 85–90 %, leaving at least 10 % headroom. Alliant AR-Comp, ReloadSwiss RS 14, Hodgdon TrailBoss rank at the top here: for .45-70 Govt. with the .458 | 405gr | Remington SP they combine a high case fill with complete burn and sit in the upper velocity band. 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.