Load Specifications
Load data in caliber .256 Mag. Gibbs with .257 | 115gr | Frontier PH HPBT bullet and 37 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-26, Alliant Reloder-16 and Somchem S365.
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% | 42,322 psi | 86% | 2730 fps | 96.6% |
| Accurate 4350 | <<locked>> | 90% | 44,556 psi | 90% | 2795 fps | 98.6% |
| ADI AR 2208 | <<locked>> | 82% | 43,540 psi | 88% | 2700 fps | 98.8% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 43,540 psi | 88% | 2726 fps | 99.7% |
| Alliant Reloder-16 | <<locked>> | 90% | 43,366 psi | 88% | 2805 fps | 98.7% |
| Alliant Reloder-17 | <<locked>> | 86% | 43,424 psi | 88% | 2828 fps | 99.7% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 42,815 psi | 87% | 2815 fps | 99.6% |
| Alliant Reloder-26 | <<locked>> | 96% | 42,076 psi | 85% | 2864 fps | 98% |
| Bofors RP3 | <<locked>> | 82% | 43,671 psi | 89% | 2736 fps | 99.7% |
| Hodgdon H380 | <<locked>> | 82% | 44,309 psi | 90% | 2740 fps | 98.1% |
| Hodgdon H414 | <<locked>> | 88% | 44,266 psi | 90% | 2792 fps | 96.1% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 42,844 psi | 87% | 2740 fps | 99.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,766 psi | 73% | 1795 fps | 100% |
| IMR 4831 | <<locked>> | 90% | 42,540 psi | 86% | 2740 fps | 98.3% |
| Lovex S065 | <<locked>> | 86% | 42,540 psi | 86% | 2680 fps | 96.9% |
| Lovex S070 | <<locked>> | 88% | 43,221 psi | 88% | 2713 fps | 96% |
| Norma URP | <<locked>> | 90% | 44,382 psi | 90% | 2792 fps | 98.5% |
| Ramshot Hunter | <<locked>> | 90% | 43,091 psi | 87% | 2779 fps | 96.7% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,289 psi | 74% | 1837 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 44,512 psi | 90% | 2720 fps | 96.7% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 43,120 psi | 87% | 2831 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 90% | 44,193 psi | 90% | 2815 fps | 98.3% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 43,743 psi | 89% | 2831 fps | 97.9% |
| Rottweil R 903 | <<locked>> | 84% | 43,569 psi | 88% | 2726 fps | 99.6% |
| Shooters World Long Rifle | <<locked>> | 86% | 42,540 psi | 86% | 2680 fps | 96.9% |
| Shooters World SW4350 | <<locked>> | 88% | 43,221 psi | 88% | 2713 fps | 96% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 42,047 psi | 85% | 2730 fps | 99% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 42,960 psi | 87% | 2605 fps | 100% |
| Somchem S355 | <<locked>> | 84% | 44,208 psi | 90% | 2730 fps | 99.6% |
| Somchem S365 | <<locked>> | 92% | 42,453 psi | 86% | 2795 fps | 100% |
| Vihtavuori N150 | <<locked>> | 84% | 42,163 psi | 86% | 2661 fps | 99.9% |
| Vihtavuori N160 | <<locked>> | 88% | 43,323 psi | 88% | 2736 fps | 98.2% |
| Vihtavuori N550 | <<locked>> | 88% | 42,685 psi | 87% | 2736 fps | 98% |
| Vihtavuori N555 | <<locked>> | 98% | 44,585 psi | 90% | 2841 fps | 99.1% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 42,801 psi | 87% | 2707 fps | 99.6% |
| Winchester 760 | <<locked>> | 88% | 44,266 psi | 90% | 2792 fps | 96.1% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 38,537 psi | 78% | 2838 fps | 99.8% |
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 3100 | <<locked>> | 96% | 39,378 psi | 80% | 2671 fps | 95.7% |
| Accurate 4350 | <<locked>> | 82% | 33,736 psi | 68% | 2562 fps | 95.7% |
| ADI AR 2208 | <<locked>> | 80% | 40,944 psi | 83% | 2648 fps | 98.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 40,915 psi | 83% | 2674 fps | 99.4% |
| Alliant Reloder-16 | 37.7 gr | 82% | 33,707 psi | 68% | 2572 fps | 95.7% |
| Alliant Reloder-17 | <<locked>> | 80% | 35,346 psi | 72% | 2644 fps | 98.1% |
| Alliant Reloder-23 | <<locked>> | 88% | 29,530 psi | 60% | 2484 fps | 95.6% |
| Alliant Reloder-26 | 46.7 gr | 92% | 36,376 psi | 74% | 2726 fps | 96.1% |
| Bofors RP3 | <<locked>> | 80% | 40,712 psi | 83% | 2677 fps | 99.4% |
| Hodgdon H380 | <<locked>> | 80% | 41,365 psi | 84% | 2680 fps | 97.5% |
| Hodgdon H414 | <<locked>> | 86% | 41,307 psi | 84% | 2730 fps | 95.2% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 29,240 psi | 59% | 2418 fps | 95.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,614 psi | 54% | 1604 fps | 100% |
| IMR 4831 | <<locked>> | 82% | 32,808 psi | 67% | 2523 fps | 95.4% |
| Lovex S065 | <<locked>> | 82% | 37,695 psi | 76% | 2575 fps | 95.5% |
| Lovex S070 | <<locked>> | 86% | 40,712 psi | 83% | 2661 fps | 95.2% |
| Norma URP | <<locked>> | 82% | 33,968 psi | 69% | 2562 fps | 95.6% |
| Ramshot Hunter | <<locked>> | 88% | 40,277 psi | 82% | 2717 fps | 95.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,166 psi | 55% | 1647 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 41,655 psi | 84% | 2664 fps | 95.9% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 37,579 psi | 76% | 2710 fps | 99.9% |
| ReloadSwiss RS 62 | <<locked>> | 82% | 33,533 psi | 68% | 2579 fps | 95.1% |
| ReloadSwiss RS 70 | <<locked>> | 84% | 35,723 psi | 72% | 2641 fps | 95.1% |
| Rottweil R 903 | <<locked>> | 80% | 38,406 psi | 78% | 2621 fps | 98.9% |
| Shooters World Long Rifle | <<locked>> | 82% | 37,695 psi | 76% | 2575 fps | 95.5% |
| Shooters World SW4350 | <<locked>> | 86% | 40,712 psi | 83% | 2661 fps | 95.2% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 39,247 psi | 80% | 2671 fps | 98.4% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 40,321 psi | 82% | 2556 fps | 100% |
| Somchem S355 | <<locked>> | 80% | 39,102 psi | 79% | 2628 fps | 98.8% |
| Somchem S365 | 37.6 gr | 80% | 28,601 psi | 58% | 2457 fps | 97% |
| Vihtavuori N150 | <<locked>> | 80% | 37,173 psi | 75% | 2559 fps | 99.4% |
| Vihtavuori N160 | <<locked>> | 80% | 33,170 psi | 67% | 2510 fps | 95.2% |
| Vihtavuori N550 | <<locked>> | 82% | 35,012 psi | 71% | 2569 fps | 95.7% |
| Vihtavuori N555 | <<locked>> | 88% | 32,068 psi | 65% | 2562 fps | 95.7% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 32,866 psi | 67% | 2487 fps | 97.4% |
| Winchester 760 | <<locked>> | 86% | 41,307 psi | 84% | 2730 fps | 95.2% |
| Winchester StaBALL HD | <<locked>> | 92% | 29,675 psi | 60% | 2569 fps | 96.4% |
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 62 powders for .256 Mag. Gibbs loaded with the .257 | 115gr | Frontier PH HPBT. Alliant Reloder-26 delivers the highest muzzle velocity at 2,864 fps; across all powders the maximum-charge window runs from 1,795 fps to 2,864 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 62 of the 62 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 115.0 gr projectile in 0.257" calls for a 1:9.0 twist; slower twists will usually not stabilise this weight. Alliant Reloder-23, Alliant Reloder-25, Bofors RP15 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, Alliant Reloder-16, Somchem S365 rank at the top here: for .256 Mag. Gibbs with the .257 | 115gr | Frontier PH HPBT they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, ADI AR 2209, ADI AR 2213, Alliant Reloder-19 burn incompletely and react more sensitively to barrel length and temperature. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.