Load Specifications
Load data in caliber .45-70 Govt. with .458 | 250gr | Barnes TSX FN FB bullet and 4 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are SNPE Vectan BA6 1/2, 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 |
|---|---|---|---|---|---|---|
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 26,136 psi | 82% | 1493 fps | 100% |
| Lovex S053 | <<locked>> | 86% | 28,601 psi | 90% | 2159 fps | 96.6% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 25,106 psi | 79% | 1522 fps | 100% |
| SNPE Vectan BA6 1/2 | <<locked>> | 88% | 28,819 psi | 90% | 2093 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 |
|---|---|---|---|---|---|---|
| Hodgdon TrailBoss | 14.6 gr | 80% | 18,739 psi | 59% | 1332 fps | 100% |
| Lovex S053 | <<locked>> | 82% | 25,425 psi | 80% | 2080 fps | 95.2% |
| ReloadSwiss RS 14 | 14.9 gr | 80% | 18,130 psi | 57% | 1362 fps | 100% |
| SNPE Vectan BA6 1/2 | 35.6 gr | 80% | 22,916 psi | 72% | 1959 fps | 99.7% |
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 4 powders for .45-70 Govt. loaded with the .458 | 250gr | Barnes TSX FN FB. Lovex S053 delivers the highest muzzle velocity at 2,159 fps; across all powders the maximum-charge window runs from 1,493 fps to 2,159 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 4 of the 4 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (220 MPa), the top charges use 79–90 %, 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. SNPE Vectan BA6 1/2, ReloadSwiss RS 14, Hodgdon TrailBoss rank at the top here: for .45-70 Govt. with the .458 | 250gr | Barnes TSX FN FB they combine a high case fill with complete burn and sit in the upper velocity band. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.