Load Specifications
Load data in caliber .257 Ackley Improved with .257 | 86gr | Remington SPRN bullet and 34 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-17, Somchem S365 and Hodgdon Hybrid 100V.
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 2495 | <<locked>> | 82% | 42,453 psi | 88% | 3045 fps | 100% |
| Accurate 4064 | <<locked>> | 84% | 42,714 psi | 89% | 3087 fps | 99.9% |
| ADI AR 2208 | <<locked>> | 84% | 41,611 psi | 86% | 3038 fps | 96.3% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 42,076 psi | 87% | 3179 fps | 96.1% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 41,292 psi | 86% | 3064 fps | 97.8% |
| Alliant Reloder-15 | <<locked>> | 82% | 41,684 psi | 86% | 3077 fps | 96.4% |
| Alliant Reloder-17 | <<locked>> | 88% | 41,263 psi | 86% | 3159 fps | 97.5% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 37,826 psi | 78% | 3054 fps | 96.3% |
| Bofors RP3 | <<locked>> | 84% | 41,205 psi | 85% | 3071 fps | 97.9% |
| Hodgdon Hybrid 100V | <<locked>> | 96% | 43,192 psi | 90% | 3127 fps | 98% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 42,554 psi | 88% | 3133 fps | 98.2% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,157 psi | 73% | 2093 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 40,959 psi | 85% | 3018 fps | 96.4% |
| IMR 4831 | <<locked>> | 94% | 42,627 psi | 88% | 3120 fps | 96.1% |
| IMR 4895 | <<locked>> | 82% | 42,699 psi | 89% | 3117 fps | 97.4% |
| Lovex S062 | <<locked>> | 84% | 43,569 psi | 90% | 3087 fps | 98.7% |
| Norma 203B | <<locked>> | 82% | 41,060 psi | 85% | 3068 fps | 96.9% |
| Ramshot Big Game | <<locked>> | 84% | 43,555 psi | 90% | 3140 fps | 97.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,462 psi | 74% | 2139 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 41,031 psi | 85% | 3169 fps | 99.4% |
| Rottweil R 902 | <<locked>> | 82% | 42,960 psi | 89% | 3054 fps | 98.5% |
| Rottweil R 903 | <<locked>> | 86% | 41,350 psi | 86% | 3064 fps | 97.7% |
| Shooters World Precision | <<locked>> | 84% | 43,569 psi | 90% | 3087 fps | 98.7% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 42,612 psi | 88% | 3123 fps | 97.2% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 41,307 psi | 86% | 2963 fps | 99.9% |
| Somchem S355 | <<locked>> | 86% | 42,090 psi | 87% | 3074 fps | 97.7% |
| Somchem S365 | <<locked>> | 96% | 42,453 psi | 88% | 3182 fps | 99% |
| Vihtavuori N135 | <<locked>> | 82% | 42,221 psi | 88% | 3041 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 42,960 psi | 89% | 3045 fps | 99.9% |
| Vihtavuori N150 | <<locked>> | 88% | 42,975 psi | 89% | 3061 fps | 99% |
| Vihtavuori N160 | <<locked>> | 92% | 43,540 psi | 90% | 3117 fps | 96% |
| Vihtavuori N540 | <<locked>> | 82% | 41,568 psi | 86% | 3028 fps | 99.6% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 41,002 psi | 85% | 3146 fps | 96.3% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 41,118 psi | 85% | 3031 fps | 97.6% |
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 2495 | <<locked>> | 80% | 39,711 psi | 82% | 2989 fps | 100% |
| Accurate 4064 | <<locked>> | 80% | 37,536 psi | 78% | 2966 fps | 99.3% |
| ADI AR 2208 | <<locked>> | 82% | 39,044 psi | 81% | 2979 fps | 95.5% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 39,218 psi | 81% | 3100 fps | 95% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 36,289 psi | 75% | 2940 fps | 96.3% |
| Alliant Reloder-15 | <<locked>> | 80% | 39,102 psi | 81% | 3015 fps | 95.6% |
| Alliant Reloder-17 | 45.2 gr | 84% | 35,911 psi | 75% | 3012 fps | 95.5% |
| Alliant Reloder-23 | <<locked>> | 98% | 35,534 psi | 74% | 2992 fps | 95.3% |
| Bofors RP3 | <<locked>> | 80% | 35,839 psi | 74% | 2940 fps | 96.3% |
| Hodgdon Hybrid 100V | 44.7 gr | 90% | 35,563 psi | 74% | 2940 fps | 95.5% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 39,639 psi | 82% | 3068 fps | 97.5% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,020 psi | 54% | 1873 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 38,682 psi | 80% | 2963 fps | 95.6% |
| IMR 4831 | <<locked>> | 92% | 39,900 psi | 83% | 3054 fps | 95.2% |
| IMR 4895 | <<locked>> | 80% | 40,030 psi | 83% | 3051 fps | 96.6% |
| Lovex S062 | <<locked>> | 80% | 38,319 psi | 79% | 2963 fps | 97.4% |
| Norma 203B | <<locked>> | 80% | 38,522 psi | 80% | 3002 fps | 96.1% |
| Ramshot Big Game | <<locked>> | 80% | 37,898 psi | 79% | 3005 fps | 95.6% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,397 psi | 55% | 1919 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 33,489 psi | 69% | 2959 fps | 97.2% |
| Rottweil R 902 | <<locked>> | 80% | 40,350 psi | 84% | 2995 fps | 97.9% |
| Rottweil R 903 | <<locked>> | 80% | 33,649 psi | 70% | 2871 fps | 95.1% |
| Shooters World Precision | <<locked>> | 80% | 38,319 psi | 79% | 2963 fps | 97.4% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 37,260 psi | 77% | 2992 fps | 95.5% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 36,201 psi | 75% | 2848 fps | 99.5% |
| Somchem S355 | <<locked>> | 80% | 34,708 psi | 72% | 2887 fps | 95.3% |
| Somchem S365 | 44.9 gr | 88% | 32,532 psi | 67% | 2917 fps | 95.9% |
| Vihtavuori N135 | <<locked>> | 80% | 39,508 psi | 82% | 2986 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 40,277 psi | 84% | 2989 fps | 99.7% |
| Vihtavuori N150 | <<locked>> | 80% | 32,880 psi | 68% | 2815 fps | 96.3% |
| Vihtavuori N160 | <<locked>> | 90% | 40,814 psi | 85% | 3054 fps | 95.2% |
| Vihtavuori N540 | <<locked>> | 80% | 38,827 psi | 81% | 2966 fps | 99.2% |
| Vihtavuori N555 | <<locked>> | 98% | 38,348 psi | 80% | 3081 fps | 95.4% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 35,955 psi | 75% | 2900 fps | 95.9% |
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 34 powders for .257 Ackley Improved loaded with the .257 | 86gr | Remington SPRN. Somchem S365 delivers the highest muzzle velocity at 3,182 fps; across all powders the maximum-charge window runs from 2,093 fps to 3,182 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 34 of the 34 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (332 MPa), the top charges use 73–90 %, leaving at least 10 % headroom. The 86.0 gr projectile in 0.257" calls for a 1:10.5 twist; slower twists will usually not stabilise this weight. Alliant Reloder-23, 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. Alliant Reloder-17, Somchem S365, Hodgdon Hybrid 100V rank at the top here: for .257 Ackley Improved with the .257 | 86gr | Remington SPRN 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.