Load Specifications
Load data in caliber .256 Mag. Gibbs with .257 | 120gr | Nosler Partition bullet and 38 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-26, ReloadSwiss RS 70 and Alliant Reloder-16.
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 3100 | <<locked>> | 98% | 44,411 psi | 90% | 2720 fps | 97.6% |
| Accurate 4350 | <<locked>> | 88% | 43,743 psi | 89% | 2726 fps | 98.8% |
| Alliant Reloder-16 | <<locked>> | 88% | 42,438 psi | 86% | 2733 fps | 98.9% |
| Alliant Reloder-17 | <<locked>> | 84% | 42,250 psi | 86% | 2749 fps | 99.7% |
| Alliant Reloder-23 | <<locked>> | 98% | 42,032 psi | 85% | 2746 fps | 99.7% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 39,320 psi | 80% | 2703 fps | 96.9% |
| Alliant Reloder-26 | <<locked>> | 96% | 44,092 psi | 89% | 2854 fps | 98.9% |
| Hodgdon H414 | <<locked>> | 86% | 43,105 psi | 87% | 2717 fps | 96.3% |
| Hodgdon Hybrid 100V | <<locked>> | 90% | 42,018 psi | 85% | 2671 fps | 99.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,013 psi | 73% | 1765 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 84% | 44,411 psi | 90% | 2664 fps | 96.4% |
| IMR 4831 | <<locked>> | 90% | 44,396 psi | 90% | 2723 fps | 99% |
| Lovex S065 | <<locked>> | 86% | 44,135 psi | 90% | 2661 fps | 97.8% |
| Lovex S070 | <<locked>> | 86% | 42,322 psi | 86% | 2644 fps | 96.3% |
| Lovex S071ᴾ | <<locked>> | 100% | 39,537 psi | 80% | 2625 fps | 96.3% |
| Norma MRP | <<locked>> | 96% | 44,005 psi | 89% | 2815 fps | 96.4% |
| Norma URP | <<locked>> | 88% | 43,207 psi | 88% | 2717 fps | 98.7% |
| Ramshot Hunter | <<locked>> | 88% | 41,974 psi | 85% | 2703 fps | 96.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,579 psi | 74% | 1804 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 82% | 41,974 psi | 85% | 2753 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 43,424 psi | 88% | 2746 fps | 98.6% |
| ReloadSwiss RS 70 | <<locked>> | 88% | 42,540 psi | 86% | 2756 fps | 98.1% |
| Rottweil R 903 | <<locked>> | 82% | 42,656 psi | 87% | 2657 fps | 99.7% |
| Shooters World Long Rifle | <<locked>> | 86% | 44,135 psi | 90% | 2661 fps | 97.8% |
| Shooters World SW4350 | <<locked>> | 86% | 42,322 psi | 86% | 2644 fps | 96.3% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 43,787 psi | 89% | 2710 fps | 99.5% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 44,483 psi | 90% | 2575 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 43,642 psi | 89% | 2608 fps | 96.4% |
| Somchem S355 | <<locked>> | 82% | 43,236 psi | 88% | 2657 fps | 99.7% |
| Somchem S365 | <<locked>> | 92% | 44,469 psi | 90% | 2776 fps | 100% |
| Somchem S385 | <<locked>> | 94% | 44,150 psi | 90% | 2710 fps | 95.9% |
| Vihtavuori N150 | <<locked>> | 84% | 43,845 psi | 89% | 2638 fps | 100% |
| Vihtavuori N160 | <<locked>> | 86% | 42,148 psi | 85% | 2661 fps | 98.4% |
| Vihtavuori N550 | <<locked>> | 88% | 44,440 psi | 90% | 2720 fps | 98.7% |
| Vihtavuori N555 | <<locked>> | 96% | 43,961 psi | 89% | 2772 fps | 99.3% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 41,597 psi | 84% | 2635 fps | 99.7% |
| Winchester 760 | <<locked>> | 86% | 43,105 psi | 87% | 2717 fps | 96.3% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 40,277 psi | 82% | 2835 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 |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 92% | 36,318 psi | 74% | 2556 fps | 95.3% |
| Accurate 4350 | <<locked>> | 80% | 33,156 psi | 67% | 2497 fps | 96% |
| Alliant Reloder-16 | 37 gr | 80% | 32,982 psi | 67% | 2507 fps | 96.1% |
| Alliant Reloder-17 | <<locked>> | 80% | 36,854 psi | 75% | 2631 fps | 98.9% |
| Alliant Reloder-23 | <<locked>> | 86% | 28,819 psi | 58% | 2418 fps | 95.9% |
| Alliant Reloder-25 | <<locked>> | 98% | 37,086 psi | 75% | 2648 fps | 96% |
| Alliant Reloder-26 | 44.9 gr | 88% | 33,185 psi | 67% | 2595 fps | 95.3% |
| Hodgdon H414 | <<locked>> | 84% | 40,219 psi | 82% | 2657 fps | 95.4% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 30,342 psi | 62% | 2405 fps | 96.8% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,876 psi | 55% | 1575 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 82% | 41,858 psi | 85% | 2612 fps | 95.7% |
| IMR 4831 | <<locked>> | 80% | 31,995 psi | 65% | 2451 fps | 95.6% |
| Lovex S065 | <<locked>> | 80% | 36,898 psi | 75% | 2510 fps | 95.8% |
| Lovex S070 | <<locked>> | 84% | 39,552 psi | 80% | 2585 fps | 95.4% |
| Lovex S071 | <<locked>> | 98% | 37,086 psi | 75% | 2572 fps | 95.5% |
| Norma MRP | <<locked>> | 94% | 41,089 psi | 83% | 2753 fps | 95.5% |
| Norma URP | <<locked>> | 80% | 33,315 psi | 68% | 2497 fps | 95.9% |
| Ramshot Hunter | <<locked>> | 84% | 36,912 psi | 75% | 2592 fps | 95.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,180 psi | 55% | 1611 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 39,175 psi | 79% | 2694 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 32,779 psi | 66% | 2510 fps | 95.4% |
| ReloadSwiss RS 70 | 41.5 gr | 82% | 34,795 psi | 71% | 2572 fps | 95.4% |
| Rottweil R 903 | <<locked>> | 80% | 40,030 psi | 81% | 2605 fps | 99.4% |
| Shooters World Long Rifle | <<locked>> | 80% | 36,898 psi | 75% | 2510 fps | 95.8% |
| Shooters World SW4350 | <<locked>> | 84% | 39,552 psi | 80% | 2585 fps | 95.4% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 40,915 psi | 83% | 2654 fps | 99.1% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 41,800 psi | 85% | 2530 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 41,060 psi | 83% | 2559 fps | 95.7% |
| Somchem S355 | <<locked>> | 80% | 40,640 psi | 82% | 2608 fps | 99.4% |
| Somchem S365 | <<locked>> | 80% | 29,907 psi | 61% | 2451 fps | 98.1% |
| Somchem S385 | <<locked>> | 92% | 41,495 psi | 84% | 2657 fps | 95.1% |
| Vihtavuori N150 | <<locked>> | 80% | 38,711 psi | 79% | 2539 fps | 99.7% |
| Vihtavuori N160 | <<locked>> | 80% | 34,664 psi | 70% | 2500 fps | 96.4% |
| Vihtavuori N550 | <<locked>> | 80% | 34,113 psi | 69% | 2497 fps | 95.9% |
| Vihtavuori N555 | <<locked>> | 84% | 29,457 psi | 60% | 2441 fps | 95.1% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 34,171 psi | 69% | 2474 fps | 98.3% |
| Winchester 760 | <<locked>> | 84% | 40,524 psi | 82% | 2664 fps | 95.5% |
| Winchester StaBALL HD | <<locked>> | 88% | 27,151 psi | 55% | 2441 fps | 95.4% |
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 38 powders for .256 Mag. Gibbs loaded with the .257 | 120gr | Nosler Partition. Alliant Reloder-26 delivers the highest muzzle velocity at 2,854 fps; across all powders the maximum-charge window runs from 1,765 fps to 2,854 fps. Alliant Reloder-25 gives the best case fill at 100 %, and 38 of the 38 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (340 MPa), the top charges use 73–90 %, leaving at least 10 % headroom. The 120.0 gr projectile in 0.257" calls for a 1:10.0 twist; slower twists will usually not stabilise this weight. Alliant Reloder-25, Hodgdon TrailBoss, Lovex S071 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 Reloder-26, ReloadSwiss RS 70, Alliant Reloder-16 rank at the top here: for .256 Mag. Gibbs with the .257 | 120gr | Nosler Partition 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.