Load Specifications
Load data in caliber .256 Mag. Gibbs with .257 | 115gr | Barnes X S bullet and 29 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-26, Winchester StaBALL HD 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>> | 96% | 43,758 psi | 89% | 2736 fps | 96.9% |
| Accurate 4350 | <<locked>> | 86% | 42,989 psi | 87% | 2743 fps | 98.3% |
| Alliant Reloder-16 | <<locked>> | 88% | 43,613 psi | 88% | 2789 fps | 98.7% |
| Alliant Reloder-17 | <<locked>> | 84% | 43,874 psi | 89% | 2818 fps | 99.7% |
| Alliant Reloder-23 | <<locked>> | 98% | 43,511 psi | 88% | 2808 fps | 99.7% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 40,886 psi | 83% | 2766 fps | 96.7% |
| Alliant Reloder-26 | <<locked>> | 94% | 42,772 psi | 87% | 2861 fps | 98.1% |
| Hodgdon H414 | <<locked>> | 86% | 44,396 psi | 90% | 2776 fps | 96.1% |
| Hodgdon Hybrid 100V | <<locked>> | 90% | 43,627 psi | 88% | 2736 fps | 99.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,405 psi | 74% | 1798 fps | 100% |
| IMR 4831 | <<locked>> | 88% | 43,352 psi | 88% | 2736 fps | 98.4% |
| Lovex S065 | <<locked>> | 84% | 43,511 psi | 88% | 2677 fps | 97.1% |
| Lovex S070 | <<locked>> | 86% | 43,976 psi | 89% | 2703 fps | 96.1% |
| Lovex S071ᴾ | <<locked>> | 100% | 41,698 psi | 85% | 2697 fps | 96.4% |
| Norma URP | <<locked>> | 86% | 42,018 psi | 85% | 2726 fps | 98% |
| Ramshot Hunter | <<locked>> | 88% | 43,569 psi | 88% | 2766 fps | 96.8% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,043 psi | 75% | 1841 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 82% | 43,569 psi | 88% | 2818 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 42,163 psi | 86% | 2753 fps | 97.9% |
| ReloadSwiss RS 70 | <<locked>> | 88% | 43,903 psi | 89% | 2815 fps | 97.9% |
| Shooters World Long Rifle | <<locked>> | 84% | 43,511 psi | 88% | 2677 fps | 97.1% |
| Shooters World SW4350 | <<locked>> | 86% | 43,976 psi | 89% | 2703 fps | 96.1% |
| Somchem S365 | <<locked>> | 90% | 43,236 psi | 88% | 2789 fps | 100% |
| Vihtavuori N150 | <<locked>> | 82% | 43,033 psi | 87% | 2654 fps | 99.9% |
| Vihtavuori N160 | <<locked>> | 86% | 43,801 psi | 89% | 2723 fps | 98.3% |
| Vihtavuori N550 | <<locked>> | 86% | 43,395 psi | 88% | 2730 fps | 98.1% |
| Vihtavuori N555 | <<locked>> | 94% | 43,062 psi | 87% | 2792 fps | 98.9% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 43,120 psi | 87% | 2697 fps | 99.6% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 41,959 psi | 85% | 2900 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% | 38,537 psi | 78% | 2628 fps | 95.4% |
| Accurate 4350 | <<locked>> | 80% | 35,375 psi | 72% | 2575 fps | 96.2% |
| Alliant Reloder-16 | 36.8 gr | 80% | 34,650 psi | 70% | 2575 fps | 96.1% |
| Alliant Reloder-17 | <<locked>> | 80% | 38,537 psi | 78% | 2700 fps | 98.9% |
| Alliant Reloder-23 | <<locked>> | 84% | 29,211 psi | 59% | 2448 fps | 95.3% |
| Alliant Reloder-25 | <<locked>> | 98% | 38,711 psi | 79% | 2710 fps | 95.8% |
| Alliant Reloder-26 | 44.6 gr | 88% | 35,114 psi | 71% | 2671 fps | 95.4% |
| Hodgdon H414 | <<locked>> | 84% | 41,887 psi | 85% | 2720 fps | 95.3% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 32,213 psi | 65% | 2477 fps | 97% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,267 psi | 55% | 1608 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 34,098 psi | 69% | 2530 fps | 95.9% |
| Lovex S065 | <<locked>> | 80% | 38,624 psi | 78% | 2572 fps | 95.8% |
| Lovex S070 | <<locked>> | 84% | 41,582 psi | 84% | 2654 fps | 95.4% |
| Lovex S071 | <<locked>> | 98% | 39,320 psi | 80% | 2648 fps | 95.6% |
| Norma URP | <<locked>> | 80% | 34,940 psi | 71% | 2562 fps | 95.9% |
| Ramshot Hunter | <<locked>> | 84% | 38,421 psi | 78% | 2654 fps | 95.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,920 psi | 57% | 1650 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 40,770 psi | 83% | 2762 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 34,592 psi | 70% | 2579 fps | 95.5% |
| ReloadSwiss RS 70 | <<locked>> | 82% | 36,289 psi | 74% | 2635 fps | 95.3% |
| Shooters World Long Rifle | <<locked>> | 80% | 38,624 psi | 78% | 2572 fps | 95.8% |
| Shooters World SW4350 | <<locked>> | 84% | 41,582 psi | 84% | 2654 fps | 95.4% |
| Somchem S365 | <<locked>> | 80% | 31,763 psi | 64% | 2523 fps | 98.2% |
| Vihtavuori N150 | <<locked>> | 80% | 40,292 psi | 82% | 2602 fps | 99.7% |
| Vihtavuori N160 | <<locked>> | 80% | 36,245 psi | 74% | 2562 fps | 96.3% |
| Vihtavuori N550 | <<locked>> | 80% | 36,085 psi | 73% | 2569 fps | 96% |
| Vihtavuori N555 | <<locked>> | 84% | 31,763 psi | 64% | 2530 fps | 95.6% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 35,607 psi | 72% | 2533 fps | 98.3% |
| Winchester StaBALL HD | 42.9 gr | 88% | 29,370 psi | 60% | 2533 fps | 96.1% |
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 29 powders for .256 Mag. Gibbs loaded with the .257 | 115gr | Barnes X S. Winchester StaBALL HD delivers the highest muzzle velocity at 2,900 fps; across all powders the maximum-charge window runs from 1,798 fps to 2,900 fps. Alliant Reloder-25 gives the best case fill at 100 %, and 29 of the 29 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (340 MPa), the top charges use 74–90 %, leaving at least 10 % headroom. The 115.0 gr projectile in 0.257" calls for a 1:9.5 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, Winchester StaBALL HD, Alliant Reloder-16 rank at the top here: for .256 Mag. Gibbs with the .257 | 115gr | Barnes X S 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.