Load Specifications
Load data in caliber .45-70 Govt. with .458 | 500gr | Remington FMC RN bullet and 8 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Accurate 2495, Vihtavuori N135 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: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 84% | 27,905 psi | 87% | 1562 fps | 97.5% |
| Accurate 2495 | <<locked>> | 94% | 27,470 psi | 86% | 1627 fps | 98.1% |
| Alliant AR-Comp | <<locked>> | 86% | 27,456 psi | 86% | 1601 fps | 99.3% |
| Hodgdon TrailBoss | <<locked>> | 92% | 28,079 psi | 88% | 1014 fps | 100% |
| IMR 3031 | <<locked>> | 88% | 27,949 psi | 88% | 1614 fps | 96.4% |
| ReloadSwiss RS 14 | <<locked>> | 94% | 28,805 psi | 90% | 1053 fps | 100% |
| Vihtavuori N133 | <<locked>> | 84% | 27,369 psi | 86% | 1522 fps | 96.9% |
| Vihtavuori N135 | <<locked>> | 92% | 28,369 psi | 89% | 1608 fps | 97.8% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 80% | 24,613 psi | 77% | 1499 fps | 96.2% |
| Accurate 2495 | 43.2 gr | 86% | 21,176 psi | 66% | 1503 fps | 95.4% |
| Alliant AR-Comp | <<locked>> | 80% | 23,076 psi | 72% | 1509 fps | 97.9% |
| Hodgdon TrailBoss | <<locked>> | 80% | 23,148 psi | 73% | 945 fps | 100% |
| IMR 3031 | <<locked>> | 86% | 26,339 psi | 83% | 1581 fps | 95.6% |
| ReloadSwiss RS 14 | 14.1 gr | 80% | 23,061 psi | 72% | 968 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 24,439 psi | 77% | 1463 fps | 95.6% |
| Vihtavuori N135 | 40.8 gr | 84% | 22,481 psi | 70% | 1483 fps | 95.1% |
Recommended = one of the top powders for this cartridge and bullet combination.
This overview compares 8 powders for .45-70 Govt. loaded with the .458 | 500gr | Remington FMC RN. Accurate 2495 delivers the highest muzzle velocity at 1,627 fps; across all powders the maximum-charge window runs from 1,014 fps to 1,627 fps. Accurate 2495 gives the best case fill at 94 %, and 8 of the 8 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (220 MPa), the top charges use 86–90 %, leaving at least 10 % headroom. Accurate 2495, Vihtavuori N135, ReloadSwiss RS 14 rank at the top here: for .45-70 Govt. with the .458 | 500gr | Remington FMC RN 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.