Load Specifications
Load data in caliber .257 Ackley Improved with .257 | 75gr | Sierra HP Varminter bullet and 30 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 60, Alliant Reloder-17 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.
A valid access license is required to use the Personalized Load Calculator.
You can find more information in our FAQ: How can I use the Personalized Load Calculator?
Max Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2495 | <<locked>> | 84% | 43,279 psi | 90% | 3255 fps | 100% |
| Accurate 4064 | <<locked>> | 84% | 40,770 psi | 85% | 3232 fps | 99.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 86% | 42,206 psi | 88% | 3271 fps | 97.1% |
| Alliant Reloder-17 | <<locked>> | 90% | 42,511 psi | 88% | 3366 fps | 96.7% |
| Bofors RP3 | <<locked>> | 86% | 42,192 psi | 88% | 3274 fps | 97.2% |
| Hodgdon Hybrid 100V | <<locked>> | 96% | 41,263 psi | 86% | 3258 fps | 96.4% |
| Hodgdon LEVERevolution | <<locked>> | 84% | 43,511 psi | 90% | 3343 fps | 97.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 34,838 psi | 72% | 2254 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 43,105 psi | 89% | 3268 fps | 96.9% |
| Lovex D073.6 | <<locked>> | 82% | 43,468 psi | 90% | 3291 fps | 99% |
| Lovex S062 | <<locked>> | 84% | 42,076 psi | 87% | 3238 fps | 97.4% |
| Norma 201 | <<locked>> | 82% | 43,598 psi | 90% | 3264 fps | 97.8% |
| Norma 203B | <<locked>> | 84% | 41,989 psi | 87% | 3271 fps | 96% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,056 psi | 73% | 2300 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 88% | 42,134 psi | 87% | 3379 fps | 98.9% |
| Rottweil R 902 | <<locked>> | 82% | 41,191 psi | 85% | 3199 fps | 97.2% |
| Rottweil R 903 | <<locked>> | 88% | 42,308 psi | 88% | 3268 fps | 96.9% |
| Shooters World Match Rifle | <<locked>> | 82% | 43,468 psi | 90% | 3291 fps | 99% |
| Shooters World Precision | <<locked>> | 84% | 42,076 psi | 87% | 3238 fps | 97.4% |
| SNPE Vectan SP 11 | <<locked>> | 88% | 43,598 psi | 90% | 3327 fps | 96.4% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 43,105 psi | 89% | 3268 fps | 96.3% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 42,409 psi | 88% | 3169 fps | 99.8% |
| Somchem S355 | <<locked>> | 88% | 42,888 psi | 89% | 3274 fps | 96.8% |
| Somchem S365 | <<locked>> | 98% | 43,410 psi | 90% | 3379 fps | 98.4% |
| Vihtavuori N135 | <<locked>> | 84% | 43,062 psi | 89% | 3258 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 41,292 psi | 86% | 3196 fps | 99.3% |
| Vihtavuori N150 | <<locked>> | 88% | 41,307 psi | 86% | 3202 fps | 97.8% |
| Vihtavuori N540 | <<locked>> | 84% | 42,772 psi | 89% | 3238 fps | 99.3% |
| Winchester 6.5 StaBALL | <<locked>> | 92% | 42,627 psi | 88% | 3235 fps | 97% |
| Winchester StaBALL Match | <<locked>> | 82% | 42,380 psi | 88% | 3268 fps | 96.8% |
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 2495 | <<locked>> | 80% | 37,855 psi | 79% | 3133 fps | 99.9% |
| Accurate 4064 | <<locked>> | 80% | 35,708 psi | 74% | 3100 fps | 98.2% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 37,130 psi | 77% | 3140 fps | 95.4% |
| Alliant Reloder-17 | 50.1 gr | 88% | 39,552 psi | 82% | 3284 fps | 95.6% |
| Bofors RP3 | <<locked>> | 82% | 36,724 psi | 76% | 3136 fps | 95.4% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 38,827 psi | 81% | 3196 fps | 95.5% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 37,985 psi | 79% | 3202 fps | 95.8% |
| Hodgdon TrailBoss | <<locked>> | 80% | 25,759 psi | 53% | 2018 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 40,321 psi | 84% | 3202 fps | 96% |
| Lovex D073.6 | <<locked>> | 80% | 40,582 psi | 84% | 3222 fps | 98.5% |
| Lovex S062 | <<locked>> | 80% | 36,999 psi | 77% | 3107 fps | 95.9% |
| Norma 201 | <<locked>> | 80% | 40,770 psi | 85% | 3196 fps | 97.1% |
| Norma 203B | <<locked>> | 82% | 39,276 psi | 81% | 3202 fps | 95.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,020 psi | 54% | 2067 fps | 100% |
| ReloadSwiss RS 60 | 46.7 gr | 82% | 34,330 psi | 71% | 3146 fps | 96.1% |
| Rottweil R 902 | <<locked>> | 80% | 38,754 psi | 80% | 3136 fps | 96.5% |
| Rottweil R 903 | <<locked>> | 84% | 36,811 psi | 76% | 3130 fps | 95% |
| Shooters World Match Rifle | <<locked>> | 80% | 40,582 psi | 84% | 3222 fps | 98.5% |
| Shooters World Precision | <<locked>> | 80% | 36,999 psi | 77% | 3107 fps | 95.9% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 40,799 psi | 85% | 3258 fps | 95.5% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 40,335 psi | 84% | 3202 fps | 95.4% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 34,896 psi | 72% | 2992 fps | 98.6% |
| Somchem S355 | <<locked>> | 84% | 37,739 psi | 78% | 3143 fps | 95.1% |
| Somchem S365 | 49.7 gr | 92% | 35,578 psi | 74% | 3173 fps | 95.8% |
| Vihtavuori N135 | <<locked>> | 80% | 37,898 psi | 79% | 3136 fps | 99.9% |
| Vihtavuori N140 | <<locked>> | 80% | 38,827 psi | 81% | 3136 fps | 98.9% |
| Vihtavuori N150 | <<locked>> | 82% | 33,591 psi | 70% | 3002 fps | 95.2% |
| Vihtavuori N540 | <<locked>> | 80% | 37,449 psi | 78% | 3110 fps | 98.2% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 37,057 psi | 77% | 3091 fps | 95% |
| Winchester StaBALL Match | <<locked>> | 80% | 39,595 psi | 82% | 3199 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 30 powders for .257 Ackley Improved loaded with the .257 | 75gr | Sierra HP Varminter. ReloadSwiss RS 60 delivers the highest muzzle velocity at 3,379 fps; across all powders the maximum-charge window runs from 2,254 fps to 3,379 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 30 of the 30 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (332 MPa), the top charges use 72–90 %, leaving at least 10 % headroom. 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. ReloadSwiss RS 60, Alliant Reloder-17, Somchem S365 rank at the top here: for .257 Ackley Improved with the .257 | 75gr | Sierra HP Varminter 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.