Load Specifications
Load data in caliber .45-70 Govt. with .458 | 405gr | Rim Rock RNFP Top Shelf bullet and 9 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 |
|---|---|---|---|---|---|---|
| ADI AR 2207 | <<locked>> | 82% | 27,818 psi | 87% | 1749 fps | 99.3% |
| Alliant AR-Comp | <<locked>> | 96% | 28,500 psi | 89% | 1804 fps | 97.3% |
| Alliant Reloder-10x | <<locked>> | 88% | 27,267 psi | 85% | 1755 fps | 96% |
| Hodgdon TrailBoss | <<locked>> | 98% | 28,195 psi | 88% | 1155 fps | 100% |
| IMR 4198 | <<locked>> | 84% | 27,804 psi | 87% | 1703 fps | 96.7% |
| Norma 200 | <<locked>> | 86% | 28,587 psi | 90% | 1778 fps | 97.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 28,427 psi | 89% | 1194 fps | 100% |
| Vihtavuori N120 | <<locked>> | 82% | 28,239 psi | 89% | 1729 fps | 99.8% |
| Vihtavuori N130 | <<locked>> | 90% | 28,761 psi | 90% | 1732 fps | 96% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AR 2207 | <<locked>> | 80% | 25,991 psi | 81% | 1713 fps | 98.9% |
| Alliant AR-Comp | 45.6 gr | 92% | 25,077 psi | 79% | 1729 fps | 95.6% |
| Alliant Reloder-10x | <<locked>> | 86% | 25,672 psi | 80% | 1722 fps | 95.3% |
| Hodgdon TrailBoss | 13.8 gr | 80% | 20,987 psi | 66% | 1040 fps | 100% |
| IMR 4198 | <<locked>> | 80% | 24,569 psi | 77% | 1631 fps | 95.1% |
| Norma 200 | <<locked>> | 80% | 23,337 psi | 73% | 1667 fps | 95.2% |
| ReloadSwiss RS 14 | 14.1 gr | 80% | 20,552 psi | 64% | 1066 fps | 100% |
| Vihtavuori N120 | <<locked>> | 80% | 26,382 psi | 83% | 1693 fps | 99.6% |
| Vihtavuori N130 | <<locked>> | 88% | 26,948 psi | 84% | 1699 fps | 95.3% |
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 21 powders for .45-70 Govt. loaded with the .458 | 405gr | Rim Rock RNFP Top Shelf. IMR 3031 delivers the highest muzzle velocity at 1,808 fps; across all powders the maximum-charge window runs from 1,155 fps to 1,808 fps. Accurate 2495 gives the best case fill at 100 %, and 21 of the 21 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (220 MPa), the top charges use 69–90 %, leaving at least 10 % headroom. Accurate 2495, ReloadSwiss RS 14, SNPE Vectan Tubal 5000 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. Alliant AR-Comp, ReloadSwiss RS 14, Hodgdon TrailBoss rank at the top here: for .45-70 Govt. 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 2015, Accurate 2495, Accurate LT-30 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.