Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 117gr | Winchester SPRN bullet and 67 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Hodgdon Retumbo, ReloadSwiss RS 76 and Vihtavuori N560.
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: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 90% | 56,260 psi | 88% | 3133 fps | 100% |
| Accurate 4350 | <<locked>> | 82% | 56,724 psi | 89% | 3159 fps | 100% |
| Accurate High Country | <<locked>> | 86% | 54,099 psi | 85% | 3235 fps | 99.3% |
| Accurate MAGPRO | <<locked>> | 88% | 54,911 psi | 86% | 3235 fps | 98.6% |
| ADI AR 2209 | <<locked>> | 88% | 57,696 psi | 90% | 3228 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 90% | 55,854 psi | 88% | 3238 fps | 99.4% |
| ADI AR 2217 | <<locked>> | 98% | 54,186 psi | 85% | 3202 fps | 99.5% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 52,518 psi | 82% | 3225 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 86% | 54,215 psi | 85% | 3163 fps | 99.7% |
| Alliant Power Pro Varmint | <<locked>> | 86% | 54,215 psi | 85% | 3163 fps | 99.7% |
| Alliant Reloder-16 | <<locked>> | 84% | 57,609 psi | 90% | 3215 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 88% | 57,116 psi | 90% | 3212 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 90% | 56,246 psi | 88% | 3235 fps | 99.9% |
| Alliant Reloder-23 | <<locked>> | 90% | 54,012 psi | 85% | 3140 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 96% | 57,725 psi | 90% | 3268 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 86% | 54,389 psi | 85% | 3225 fps | 100% |
| Alliant Reloder-33ᴾ | <<locked>> | 100% | 55,579 psi | 87% | 3291 fps | 97.3% |
| Baschieri & Pellagri 109 | <<locked>> | 92% | 56,594 psi | 89% | 3189 fps | 97.6% |
| Bofors RP15 | <<locked>> | 92% | 55,434 psi | 87% | 3219 fps | 99.8% |
| Bofors RP30 | <<locked>> | 98% | 57,450 psi | 90% | 3278 fps | 99.8% |
| Bofors RP5 | <<locked>> | 90% | 56,246 psi | 88% | 3235 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 96% | 55,738 psi | 87% | 3232 fps | 99.8% |
| Hodgdon H4831 | <<locked>> | 88% | 55,158 psi | 86% | 3166 fps | 98.9% |
| Hodgdon H4831 SC | <<locked>> | 88% | 54,128 psi | 85% | 3150 fps | 98.7% |
| Hodgdon Hybrid 100V | <<locked>> | 84% | 54,157 psi | 85% | 3074 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 56,753 psi | 89% | 3360 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,550 psi | 59% | 2037 fps | 100% |
| IMR 4350 | <<locked>> | 84% | 56,463 psi | 88% | 3143 fps | 100% |
| IMR 4831 | <<locked>> | 84% | 56,898 psi | 89% | 3146 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 88% | 55,883 psi | 88% | 3146 fps | 99.1% |
| IMR 7828 SSC | <<locked>> | 90% | 53,896 psi | 84% | 3212 fps | 99.2% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 47,892 psi | 75% | 3127 fps | 98.6% |
| Lovex S065 | <<locked>> | 82% | 56,710 psi | 89% | 3120 fps | 100% |
| Lovex S070 | <<locked>> | 82% | 55,027 psi | 86% | 3117 fps | 100% |
| Lovex S071 | <<locked>> | 96% | 57,580 psi | 90% | 3153 fps | 100% |
| Norma 204 | <<locked>> | 84% | 57,725 psi | 90% | 3205 fps | 99.9% |
| Norma 217ᴾ | <<locked>> | 100% | 48,675 psi | 76% | 3153 fps | 99.9% |
| Norma MRP | <<locked>> | 88% | 56,275 psi | 88% | 3255 fps | 100% |
| Norma URP | <<locked>> | 82% | 54,810 psi | 86% | 3133 fps | 100% |
| Ramshot Grand | <<locked>> | 90% | 54,897 psi | 86% | 3238 fps | 99.6% |
| Ramshot Hunter | <<locked>> | 84% | 57,551 psi | 90% | 3202 fps | 100% |
| Ramshot Magnum | <<locked>> | 94% | 57,624 psi | 90% | 3228 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,334 psi | 60% | 2083 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 82% | 56,826 psi | 89% | 3179 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 82% | 55,245 psi | 87% | 3205 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 53,417 psi | 84% | 3281 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 57,014 psi | 89% | 3304 fps | 99.1% |
| Rottweil R 904 | <<locked>> | 86% | 54,723 psi | 86% | 3133 fps | 99.2% |
| Rottweil R 905 | <<locked>> | 88% | 56,739 psi | 89% | 3202 fps | 99.9% |
| Shooters World Long Rifle | <<locked>> | 82% | 56,710 psi | 89% | 3120 fps | 100% |
| Shooters World SW4350 | <<locked>> | 82% | 55,027 psi | 86% | 3117 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 82% | 55,666 psi | 87% | 3068 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 56,333 psi | 88% | 3199 fps | 99.9% |
| Somchem S361 | <<locked>> | 86% | 56,115 psi | 88% | 3120 fps | 99% |
| Somchem S365 | <<locked>> | 84% | 56,057 psi | 88% | 3140 fps | 100% |
| Somchem S385 | <<locked>> | 88% | 57,232 psi | 90% | 3169 fps | 100% |
| Vihtavuori N160 | <<locked>> | 82% | 56,521 psi | 89% | 3127 fps | 100% |
| Vihtavuori N165 | <<locked>> | 92% | 57,029 psi | 89% | 3153 fps | 100% |
| Vihtavuori N550 | <<locked>> | 82% | 55,825 psi | 87% | 3133 fps | 100% |
| Vihtavuori N555 | <<locked>> | 88% | 56,173 psi | 88% | 3169 fps | 100% |
| Vihtavuori N560 | <<locked>> | 88% | 55,782 psi | 87% | 3251 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 94% | 56,347 psi | 88% | 3238 fps | 99.3% |
| Vihtavuori N568 | <<locked>> | 98% | 57,653 psi | 90% | 3304 fps | 98.8% |
| Vihtavuori N570 | <<locked>> | 98% | 54,578 psi | 86% | 3297 fps | 96.7% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 55,999 psi | 88% | 3074 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 92% | 57,377 psi | 90% | 3291 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 57,058 psi | 89% | 3166 fps | 99.9% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 80% | 40,001 psi | 63% | 2831 fps | 99.3% |
| Accurate 4350 | <<locked>> | 80% | 52,881 psi | 83% | 3097 fps | 100% |
| Accurate High Country | <<locked>> | 80% | 43,627 psi | 68% | 3022 fps | 97.3% |
| Accurate MAGPRO | <<locked>> | 80% | 41,336 psi | 65% | 2956 fps | 95.2% |
| ADI AR 2209 | <<locked>> | 80% | 43,961 psi | 69% | 2972 fps | 98.3% |
| ADI AR 2213 | <<locked>> | 80% | 39,450 psi | 62% | 2900 fps | 95.8% |
| ADI AR 2217 | <<locked>> | 88% | 38,406 psi | 60% | 2871 fps | 95.9% |
| ADI AR 2225 | <<locked>> | 84% | 30,661 psi | 48% | 2700 fps | 95.7% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 44,338 psi | 69% | 2972 fps | 98.3% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 44,338 psi | 69% | 2972 fps | 98.3% |
| Alliant Reloder-16 | <<locked>> | 80% | 50,517 psi | 79% | 3100 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 43,932 psi | 69% | 2966 fps | 98.3% |
| Alliant Reloder-22 | <<locked>> | 80% | 40,059 psi | 63% | 2910 fps | 97.4% |
| Alliant Reloder-23 | <<locked>> | 80% | 38,740 psi | 61% | 2858 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 33,388 psi | 52% | 2772 fps | 98.5% |
| Alliant Reloder-26 | <<locked>> | 80% | 43,497 psi | 68% | 3028 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 96% | 47,790 psi | 75% | 3143 fps | 95.3% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 46,818 psi | 73% | 2999 fps | 95.1% |
| Bofors RP15 | <<locked>> | 80% | 37,202 psi | 58% | 2838 fps | 96.4% |
| Bofors RP30 | <<locked>> | 84% | 35,520 psi | 56% | 2822 fps | 95% |
| Bofors RP5 | <<locked>> | 80% | 40,059 psi | 63% | 2910 fps | 97.4% |
| Hodgdon H1000 | <<locked>> | 84% | 36,550 psi | 57% | 2825 fps | 95.9% |
| Hodgdon H4831 | <<locked>> | 80% | 41,887 psi | 66% | 2904 fps | 96% |
| Hodgdon H4831 SC | <<locked>> | 80% | 41,307 psi | 65% | 2890 fps | 95.8% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 47,514 psi | 74% | 2966 fps | 100% |
| Hodgdon Retumbo | 58.1 gr | 80% | 32,561 psi | 51% | 2795 fps | 95.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,123 psi | 44% | 1824 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 49,676 psi | 78% | 3025 fps | 99.7% |
| IMR 4831 | <<locked>> | 80% | 50,140 psi | 79% | 3035 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 43,250 psi | 68% | 2900 fps | 96.6% |
| IMR 7828 SSC | <<locked>> | 80% | 38,101 psi | 60% | 2877 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 92% | 36,477 psi | 57% | 2864 fps | 95.2% |
| Lovex S065 | <<locked>> | 80% | 53,345 psi | 84% | 3064 fps | 100% |
| Lovex S070 | <<locked>> | 80% | 51,721 psi | 81% | 3061 fps | 100% |
| Lovex S071 | <<locked>> | 80% | 34,505 psi | 54% | 2700 fps | 98% |
| Norma 204 | <<locked>> | 80% | 50,314 psi | 79% | 3077 fps | 99.2% |
| Norma 217 | <<locked>> | 88% | 31,850 psi | 50% | 2756 fps | 95.6% |
| Norma MRP | <<locked>> | 80% | 42,177 psi | 66% | 2986 fps | 99% |
| Norma URP | <<locked>> | 80% | 51,430 psi | 81% | 3081 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 37,782 psi | 59% | 2884 fps | 95.8% |
| Ramshot Hunter | <<locked>> | 80% | 50,328 psi | 79% | 3081 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 33,910 psi | 53% | 2753 fps | 96.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,877 psi | 45% | 1870 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 53,098 psi | 83% | 3120 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 51,474 psi | 81% | 3143 fps | 100% |
| ReloadSwiss RS 76 | 62.2 gr | 80% | 31,749 psi | 50% | 2766 fps | 96.1% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 42,032 psi | 66% | 3012 fps | 95.8% |
| Rottweil R 904 | <<locked>> | 80% | 45,020 psi | 71% | 2946 fps | 97.6% |
| Rottweil R 905 | <<locked>> | 80% | 43,511 psi | 68% | 2953 fps | 98.3% |
| Shooters World Long Rifle | <<locked>> | 80% | 53,345 psi | 84% | 3064 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 51,721 psi | 81% | 3061 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 52,272 psi | 82% | 3012 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 43,178 psi | 68% | 2949 fps | 98.3% |
| Somchem S361 | <<locked>> | 80% | 45,934 psi | 72% | 2933 fps | 97.1% |
| Somchem S365 | <<locked>> | 80% | 48,936 psi | 77% | 3028 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 44,092 psi | 69% | 2933 fps | 99% |
| Vihtavuori N160 | <<locked>> | 80% | 52,779 psi | 83% | 3068 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 38,261 psi | 60% | 2792 fps | 97.5% |
| Vihtavuori N550 | <<locked>> | 80% | 52,243 psi | 82% | 3074 fps | 100% |
| Vihtavuori N555 | <<locked>> | 80% | 43,149 psi | 68% | 2940 fps | 100% |
| Vihtavuori N560 | 60.3 gr | 80% | 42,018 psi | 66% | 2976 fps | 96.2% |
| Vihtavuori N565 | <<locked>> | 84% | 40,074 psi | 63% | 2907 fps | 95.9% |
| Vihtavuori N568 | <<locked>> | 90% | 43,120 psi | 68% | 3025 fps | 95.5% |
| Vihtavuori N570 | <<locked>> | 96% | 50,778 psi | 80% | 3225 fps | 95.7% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 52,156 psi | 82% | 3015 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 80% | 35,940 psi | 56% | 2904 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 40,495 psi | 63% | 2851 fps | 97.5% |
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 67 powders for .257 Weath. Mag. loaded with the .257 | 117gr | Winchester SPRN. Hodgdon Retumbo delivers the highest muzzle velocity at 3,360 fps; across all powders the maximum-charge window runs from 2,037 fps to 3,360 fps. ADI AR 2225 gives the best case fill at 100 %, and 67 of the 67 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 59–90 %, leaving at least 10 % headroom. The 117.0 gr projectile in 0.257" calls for a 1:12.5 twist; slower twists will usually not stabilise this weight. ADI AR 2225, Alliant Reloder-33, 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. Hodgdon Retumbo, ReloadSwiss RS 76, Vihtavuori N560 rank at the top here: for .257 Weath. Mag. with the .257 | 117gr | Winchester 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.