Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 100gr | Frontier BTSP bullet and 74 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Winchester StaBALL HD, Norma MRP 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.
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Max Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 94% | 55,056 psi | 86% | 3320 fps | 100% |
| Accurate 4350 | <<locked>> | 86% | 56,217 psi | 88% | 3369 fps | 100% |
| Accurate High Country | <<locked>> | 92% | 56,855 psi | 89% | 3491 fps | 98.6% |
| Accurate MAGPRO | <<locked>> | 92% | 53,737 psi | 84% | 3412 fps | 96.8% |
| ADI AR 2208 | <<locked>> | 82% | 56,971 psi | 89% | 3330 fps | 100% |
| ADI AR 2209 | <<locked>> | 92% | 57,217 psi | 90% | 3428 fps | 99.2% |
| ADI AR 2213 | <<locked>> | 94% | 55,100 psi | 86% | 3428 fps | 98.1% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 49,414 psi | 77% | 3297 fps | 97.3% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 44,280 psi | 69% | 3248 fps | 98.9% |
| Alliant Power Pro Varmint | <<locked>> | 92% | 57,319 psi | 90% | 3419 fps | 99.2% |
| Alliant Reloder-16 | <<locked>> | 88% | 57,029 psi | 89% | 3432 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 82% | 54,375 psi | 85% | 3383 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 92% | 56,608 psi | 89% | 3412 fps | 99.1% |
| Alliant Reloder-22 | <<locked>> | 94% | 55,143 psi | 86% | 3422 fps | 99.1% |
| Alliant Reloder-23 | <<locked>> | 96% | 56,289 psi | 88% | 3399 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 55,753 psi | 87% | 3458 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 92% | 57,000 psi | 89% | 3494 fps | 100% |
| Bofors RP15 | <<locked>> | 96% | 54,070 psi | 85% | 3399 fps | 98.8% |
| Bofors RP30ᴾ | <<locked>> | 100% | 51,851 psi | 81% | 3383 fps | 98.1% |
| Bofors RP5 | <<locked>> | 94% | 55,143 psi | 86% | 3422 fps | 99.1% |
| Bofors RP7 | <<locked>> | 84% | 54,926 psi | 86% | 3307 fps | 99.4% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 54,723 psi | 86% | 3406 fps | 98.8% |
| Hodgdon H414 | <<locked>> | 84% | 54,114 psi | 85% | 3360 fps | 99.6% |
| Hodgdon H4350 | <<locked>> | 84% | 56,681 psi | 89% | 3379 fps | 99.2% |
| Hodgdon H4831 | <<locked>> | 92% | 55,027 psi | 86% | 3356 fps | 97.4% |
| Hodgdon H4831 SC | <<locked>> | 94% | 57,740 psi | 90% | 3406 fps | 97.9% |
| Hodgdon Hybrid 100V | <<locked>> | 90% | 57,493 psi | 90% | 3343 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 54,708 psi | 86% | 3533 fps | 99.7% |
| Hodgdon Superformance | <<locked>> | 84% | 54,679 psi | 86% | 3396 fps | 99.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,869 psi | 58% | 2169 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 56,652 psi | 89% | 3350 fps | 99.6% |
| IMR 4451 Enduron | <<locked>> | 84% | 56,376 psi | 88% | 3337 fps | 99.7% |
| IMR 4831 | <<locked>> | 88% | 56,565 psi | 89% | 3356 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 55,985 psi | 88% | 3340 fps | 97.8% |
| IMR 7828 SSC | <<locked>> | 96% | 56,507 psi | 89% | 3461 fps | 98.4% |
| Lovex S065 | <<locked>> | 86% | 57,058 psi | 89% | 3333 fps | 100% |
| Lovex S070 | <<locked>> | 86% | 55,143 psi | 86% | 3323 fps | 99.7% |
| Lovex S071ᴾ | <<locked>> | 100% | 56,188 psi | 88% | 3340 fps | 100% |
| Norma 204 | <<locked>> | 86% | 54,041 psi | 85% | 3343 fps | 98.6% |
| Norma 217ᴾ | <<locked>> | 100% | 39,697 psi | 62% | 3156 fps | 96.9% |
| Norma MRP | <<locked>> | 92% | 55,056 psi | 86% | 3448 fps | 99.7% |
| Norma URP | <<locked>> | 86% | 54,476 psi | 85% | 3346 fps | 100% |
| Ramshot Grand | <<locked>> | 96% | 57,624 psi | 90% | 3488 fps | 98.9% |
| Ramshot Hunter | <<locked>> | 88% | 57,188 psi | 90% | 3409 fps | 100% |
| Ramshot Magnum | <<locked>> | 98% | 56,202 psi | 88% | 3412 fps | 99.7% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,739 psi | 59% | 2221 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 56,391 psi | 88% | 3389 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 86% | 54,795 psi | 86% | 3422 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 55,666 psi | 87% | 3527 fps | 100% |
| ReloadSwiss RS 80ᴾ | <<locked>> | 100% | 50,502 psi | 79% | 3383 fps | 96.4% |
| Rottweil R 903 | <<locked>> | 82% | 56,304 psi | 88% | 3317 fps | 100% |
| Rottweil R 904 | <<locked>> | 90% | 54,607 psi | 86% | 3327 fps | 98% |
| Rottweil R 905 | <<locked>> | 92% | 56,057 psi | 88% | 3399 fps | 99.2% |
| Rottweil R 907 | <<locked>> | 84% | 54,926 psi | 86% | 3307 fps | 99.4% |
| Shooters World Long Rifle | <<locked>> | 86% | 57,058 psi | 89% | 3333 fps | 100% |
| Shooters World SW4350 | <<locked>> | 86% | 55,143 psi | 86% | 3323 fps | 99.7% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 55,825 psi | 87% | 3173 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 56,304 psi | 88% | 3278 fps | 99.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 92% | 55,608 psi | 87% | 3392 fps | 99.1% |
| Somchem S355 | <<locked>> | 82% | 55,724 psi | 87% | 3304 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 56,521 psi | 89% | 3317 fps | 97.7% |
| Somchem S365 | <<locked>> | 88% | 55,114 psi | 86% | 3353 fps | 100% |
| Somchem S385 | <<locked>> | 92% | 56,637 psi | 89% | 3366 fps | 99.6% |
| Vihtavuori N150 | <<locked>> | 84% | 57,276 psi | 90% | 3278 fps | 100% |
| Vihtavuori N160 | <<locked>> | 86% | 56,405 psi | 88% | 3340 fps | 100% |
| Vihtavuori N165 | <<locked>> | 96% | 56,478 psi | 89% | 3343 fps | 99.4% |
| Vihtavuori N550 | <<locked>> | 86% | 55,622 psi | 87% | 3343 fps | 100% |
| Vihtavuori N555 | <<locked>> | 92% | 54,853 psi | 86% | 3369 fps | 100% |
| Vihtavuori N560 | <<locked>> | 92% | 54,839 psi | 86% | 3435 fps | 97.7% |
| Vihtavuori N565 | <<locked>> | 98% | 54,665 psi | 86% | 3406 fps | 97.9% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 56,101 psi | 88% | 3287 fps | 100% |
| Winchester 760 | <<locked>> | 84% | 54,360 psi | 85% | 3366 fps | 99.6% |
| Winchester StaBALL HD | <<locked>> | 96% | 54,172 psi | 85% | 3484 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 94% | 56,971 psi | 89% | 3363 fps | 99.2% |
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% | 34,098 psi | 53% | 2871 fps | 96.2% |
| Accurate 4350 | <<locked>> | 80% | 45,730 psi | 72% | 3176 fps | 99.8% |
| Accurate High Country | <<locked>> | 84% | 42,728 psi | 67% | 3196 fps | 95.1% |
| Accurate MAGPRO | <<locked>> | 90% | 50,038 psi | 78% | 3340 fps | 95.9% |
| ADI AR 2208 | <<locked>> | 80% | 53,432 psi | 84% | 3268 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 40,799 psi | 64% | 3087 fps | 95.6% |
| ADI AR 2213 | <<locked>> | 88% | 44,759 psi | 70% | 3209 fps | 95.5% |
| ADI AR 2217 | <<locked>> | 96% | 43,076 psi | 68% | 3156 fps | 95.3% |
| ADI AR 2225 | <<locked>> | 94% | 36,187 psi | 57% | 3031 fps | 96.1% |
| Alliant Power Pro Varmint | <<locked>> | 82% | 41,147 psi | 64% | 3091 fps | 95.8% |
| Alliant Reloder-16 | <<locked>> | 80% | 43,598 psi | 68% | 3179 fps | 99.8% |
| Alliant Reloder-17 | <<locked>> | 80% | 50,546 psi | 79% | 3317 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 40,756 psi | 64% | 3081 fps | 95.7% |
| Alliant Reloder-22 | <<locked>> | 84% | 38,972 psi | 61% | 3074 fps | 95.2% |
| Alliant Reloder-23 | <<locked>> | 80% | 32,706 psi | 51% | 2907 fps | 98.9% |
| Alliant Reloder-25 | <<locked>> | 82% | 30,472 psi | 48% | 2854 fps | 95.1% |
| Alliant Reloder-26 | <<locked>> | 80% | 35,839 psi | 56% | 3054 fps | 98.2% |
| Bofors RP15 | <<locked>> | 88% | 41,350 psi | 65% | 3130 fps | 95.9% |
| Bofors RP30 | <<locked>> | 94% | 41,843 psi | 66% | 3169 fps | 95.4% |
| Bofors RP5 | <<locked>> | 84% | 38,972 psi | 61% | 3074 fps | 95.2% |
| Bofors RP7 | <<locked>> | 80% | 48,269 psi | 76% | 3179 fps | 98.5% |
| Hodgdon H1000 | <<locked>> | 92% | 41,365 psi | 65% | 3117 fps | 95.4% |
| Hodgdon H414 | <<locked>> | 80% | 47,224 psi | 74% | 3225 fps | 98.8% |
| Hodgdon H4350 | <<locked>> | 80% | 49,864 psi | 78% | 3248 fps | 98.3% |
| Hodgdon H4831 | <<locked>> | 88% | 47,848 psi | 75% | 3215 fps | 95.8% |
| Hodgdon H4831 SC | <<locked>> | 88% | 46,949 psi | 74% | 3199 fps | 95.5% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 41,104 psi | 64% | 3048 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 38,856 psi | 61% | 3156 fps | 95.8% |
| Hodgdon Superformance | <<locked>> | 80% | 47,065 psi | 74% | 3248 fps | 98.6% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,659 psi | 43% | 1946 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 43,874 psi | 69% | 3097 fps | 97.6% |
| IMR 4451 Enduron | <<locked>> | 80% | 49,690 psi | 78% | 3212 fps | 99% |
| IMR 4831 | <<locked>> | 80% | 43,395 psi | 68% | 3110 fps | 99.7% |
| IMR 4955 Enduron | <<locked>> | 86% | 46,224 psi | 72% | 3150 fps | 95.5% |
| IMR 7828 SSC | <<locked>> | 88% | 42,975 psi | 67% | 3179 fps | 95% |
| Lovex S065 | <<locked>> | 80% | 47,369 psi | 74% | 3156 fps | 99.5% |
| Lovex S070 | <<locked>> | 80% | 45,672 psi | 72% | 3140 fps | 98.6% |
| Lovex S071 | <<locked>> | 84% | 33,431 psi | 52% | 2851 fps | 95.9% |
| Norma 204 | <<locked>> | 80% | 43,830 psi | 69% | 3133 fps | 96.4% |
| Norma 217 | <<locked>> | 98% | 37,057 psi | 58% | 3084 fps | 95.9% |
| Norma MRP | 58.8 gr | 80% | 35,505 psi | 56% | 3012 fps | 95.3% |
| Norma URP | <<locked>> | 80% | 44,846 psi | 70% | 3159 fps | 99.7% |
| Ramshot Grand | <<locked>> | 88% | 42,931 psi | 67% | 3189 fps | 95.5% |
| Ramshot Hunter | <<locked>> | 80% | 43,656 psi | 68% | 3150 fps | 98.7% |
| Ramshot Magnum | <<locked>> | 88% | 38,464 psi | 60% | 3048 fps | 96% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,326 psi | 44% | 1995 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 45,745 psi | 72% | 3196 fps | 99.7% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 43,990 psi | 69% | 3212 fps | 99.6% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 35,694 psi | 56% | 3054 fps | 95.7% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 46,789 psi | 73% | 3304 fps | 95.3% |
| Rottweil R 903 | <<locked>> | 80% | 52,736 psi | 83% | 3258 fps | 100% |
| Rottweil R 904 | <<locked>> | 84% | 45,049 psi | 71% | 3133 fps | 95.8% |
| Rottweil R 905 | <<locked>> | 82% | 39,914 psi | 63% | 3061 fps | 95.6% |
| Rottweil R 907 | <<locked>> | 80% | 48,269 psi | 76% | 3179 fps | 98.5% |
| Shooters World Long Rifle | <<locked>> | 80% | 47,369 psi | 74% | 3156 fps | 99.5% |
| Shooters World SW4350 | <<locked>> | 80% | 45,672 psi | 72% | 3140 fps | 98.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 52,533 psi | 82% | 3123 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 46,282 psi | 73% | 3091 fps | 98.6% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 39,624 psi | 62% | 3054 fps | 95.4% |
| Somchem S355 | <<locked>> | 80% | 52,518 psi | 82% | 3251 fps | 100% |
| Somchem S361 | <<locked>> | 84% | 46,180 psi | 72% | 3117 fps | 95.3% |
| Somchem S365 | <<locked>> | 80% | 41,785 psi | 65% | 3110 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 38,043 psi | 60% | 2979 fps | 95.9% |
| Vihtavuori N150 | <<locked>> | 80% | 50,270 psi | 79% | 3166 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 46,253 psi | 72% | 3156 fps | 99.8% |
| Vihtavuori N165 | <<locked>> | 84% | 37,695 psi | 59% | 2959 fps | 95.4% |
| Vihtavuori N550 | <<locked>> | 80% | 45,643 psi | 72% | 3156 fps | 99.7% |
| Vihtavuori N555 | <<locked>> | 80% | 36,695 psi | 57% | 2995 fps | 98.9% |
| Vihtavuori N560 | 64.7 gr | 88% | 47,500 psi | 74% | 3287 fps | 95.9% |
| Vihtavuori N565 | <<locked>> | 92% | 44,483 psi | 70% | 3199 fps | 95.3% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 45,542 psi | 71% | 3110 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 47,471 psi | 74% | 3228 fps | 98.8% |
| Winchester StaBALL HD | 58.2 gr | 80% | 29,037 psi | 46% | 2904 fps | 98.9% |
| Winchester Supreme 780 | <<locked>> | 84% | 39,885 psi | 63% | 3018 fps | 95.4% |
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 74 powders for .257 Weath. Mag. loaded with the .257 | 100gr | Frontier BTSP. Hodgdon Retumbo delivers the highest muzzle velocity at 3,533 fps; across all powders the maximum-charge window runs from 2,169 fps to 3,533 fps. ADI AR 2217 gives the best case fill at 100 %, and 74 of the 74 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 58–90 %, leaving at least 10 % headroom. The 100.0 gr projectile in 0.257" calls for a 1:9.0 twist; slower twists will usually not stabilise this weight. ADI AR 2217, ADI AR 2225, Alliant Reloder-25 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. Winchester StaBALL HD, Norma MRP, Vihtavuori N560 rank at the top here: for .257 Weath. Mag. with the .257 | 100gr | Frontier BTSP 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.