Load Specifications
Load data in caliber .257 Ackley Improved with .257 | 87gr | Speer Hot-Cor bullet and 30 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Somchem S365, Hodgdon Hybrid 100V and Winchester 6.5 StaBALL.
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 4064 | <<locked>> | 82% | 41,829 psi | 87% | 3058 fps | 99.9% |
| ADI AR 2208 | <<locked>> | 84% | 43,308 psi | 90% | 3071 fps | 97.1% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 43,149 psi | 90% | 3100 fps | 98.5% |
| Alliant Reloder-15 | <<locked>> | 82% | 43,555 psi | 90% | 3114 fps | 97.3% |
| Alliant Reloder-16 | <<locked>> | 92% | 43,018 psi | 89% | 3169 fps | 96.7% |
| Alliant Reloder-17 | <<locked>> | 88% | 43,105 psi | 89% | 3199 fps | 98.3% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 39,842 psi | 83% | 3104 fps | 97.4% |
| Bofors RP3 | <<locked>> | 84% | 43,105 psi | 89% | 3107 fps | 98.6% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 42,409 psi | 88% | 3100 fps | 98.1% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,433 psi | 74% | 2103 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 42,772 psi | 89% | 3054 fps | 97.2% |
| IMR 4831 | <<locked>> | 92% | 42,192 psi | 88% | 3100 fps | 96.3% |
| Lovex S062 | <<locked>> | 82% | 42,757 psi | 89% | 3061 fps | 98.7% |
| Norma 203B | <<locked>> | 82% | 42,888 psi | 89% | 3100 fps | 97.7% |
| Norma URP | <<locked>> | 92% | 43,569 psi | 90% | 3150 fps | 96.5% |
| Ramshot Big Game | <<locked>> | 82% | 42,641 psi | 88% | 3110 fps | 97.5% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,766 psi | 74% | 2149 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 42,917 psi | 89% | 3209 fps | 99.8% |
| Rottweil R 903 | <<locked>> | 86% | 43,221 psi | 90% | 3100 fps | 98.4% |
| Shooters World Precision | <<locked>> | 82% | 42,757 psi | 89% | 3061 fps | 98.7% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 41,713 psi | 87% | 3094 fps | 97.3% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 42,844 psi | 89% | 2986 fps | 100% |
| Somchem S355 | <<locked>> | 84% | 41,263 psi | 86% | 3048 fps | 97.7% |
| Somchem S365 | <<locked>> | 94% | 41,945 psi | 87% | 3159 fps | 99.2% |
| Vihtavuori N150 | <<locked>> | 86% | 42,018 psi | 87% | 3031 fps | 99% |
| Vihtavuori N160 | <<locked>> | 90% | 42,757 psi | 89% | 3094 fps | 96.2% |
| Vihtavuori N540 | <<locked>> | 82% | 43,337 psi | 90% | 3058 fps | 99.9% |
| Vihtavuori N555 | <<locked>> | 98% | 40,669 psi | 84% | 3130 fps | 96.5% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 42,859 psi | 89% | 3068 fps | 98.4% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 35,650 psi | 74% | 3074 fps | 96.6% |
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 4064 | <<locked>> | 80% | 39,276 psi | 81% | 2999 fps | 99.7% |
| ADI AR 2208 | <<locked>> | 80% | 38,319 psi | 79% | 2953 fps | 95.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 37,855 psi | 79% | 2972 fps | 97.2% |
| Alliant Reloder-15 | <<locked>> | 80% | 40,683 psi | 84% | 3048 fps | 96.5% |
| Alliant Reloder-16 | <<locked>> | 90% | 40,466 psi | 84% | 3104 fps | 95.8% |
| Alliant Reloder-17 | <<locked>> | 82% | 35,172 psi | 73% | 2986 fps | 95.6% |
| Alliant Reloder-23 | <<locked>> | 96% | 35,085 psi | 73% | 2976 fps | 95.5% |
| Bofors RP3 | <<locked>> | 80% | 37,710 psi | 78% | 2979 fps | 97.3% |
| Hodgdon Hybrid 100V | 45.1 gr | 88% | 34,838 psi | 72% | 2917 fps | 95.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,295 psi | 55% | 1880 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 40,190 psi | 83% | 2995 fps | 96.5% |
| IMR 4831 | <<locked>> | 90% | 39,349 psi | 82% | 3035 fps | 95.4% |
| Lovex S062 | <<locked>> | 80% | 40,190 psi | 83% | 3002 fps | 98.2% |
| Norma 203B | <<locked>> | 80% | 40,103 psi | 83% | 3035 fps | 96.9% |
| Norma URP | <<locked>> | 90% | 40,930 psi | 85% | 3087 fps | 95.7% |
| Ramshot Big Game | <<locked>> | 80% | 39,842 psi | 83% | 3045 fps | 96.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,672 psi | 55% | 1926 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 34,983 psi | 73% | 2999 fps | 98.1% |
| Rottweil R 903 | <<locked>> | 80% | 35,476 psi | 74% | 2913 fps | 96.2% |
| Shooters World Precision | <<locked>> | 80% | 40,190 psi | 83% | 3002 fps | 98.2% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 36,376 psi | 75% | 2963 fps | 95.5% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 37,753 psi | 78% | 2874 fps | 99.8% |
| Somchem S355 | <<locked>> | 80% | 36,201 psi | 75% | 2920 fps | 96.2% |
| Somchem S365 | 45.3 gr | 86% | 31,923 psi | 66% | 2894 fps | 96% |
| Vihtavuori N150 | <<locked>> | 80% | 34,505 psi | 72% | 2851 fps | 97.2% |
| Vihtavuori N160 | <<locked>> | 88% | 40,147 psi | 83% | 3035 fps | 95.4% |
| Vihtavuori N540 | <<locked>> | 80% | 40,509 psi | 84% | 2995 fps | 99.6% |
| Vihtavuori N555 | <<locked>> | 96% | 38,101 psi | 79% | 3064 fps | 95.7% |
| Winchester 6.5 StaBALL | 46.8 gr | 82% | 32,851 psi | 68% | 2812 fps | 95% |
| Winchester StaBALL HD | <<locked>> | 98% | 33,359 psi | 69% | 2995 fps | 95.1% |
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 52 powders for .257 Ackley Improved loaded with the .257 | 87gr | Speer Hot-Cor. ReloadSwiss RS 60 delivers the highest muzzle velocity at 3,209 fps; across all powders the maximum-charge window runs from 2,103 fps to 3,209 fps. Accurate 3100 gives the best case fill at 100 %, and 52 of the 52 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (332 MPa), the top charges use 74–90 %, leaving at least 10 % headroom. The 87.0 gr projectile in 0.257" calls for a 1:14.5 twist; slower twists will usually not stabilise this weight. Accurate 3100, Alliant Reloder-23, Hodgdon TrailBoss 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. Somchem S365, Hodgdon Hybrid 100V, Winchester 6.5 StaBALL rank at the top here: for .257 Ackley Improved with the .257 | 87gr | Speer Hot-Cor they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Accurate 3100, Bofors RP7, Hodgdon H414 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.