Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 100gr | Sierra GameKing bullet and 75 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Winchester StaBALL HD, IMR 7828 SSC and Hodgdon Retumbo.
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 2700 | <<locked>> | 82% | 57,116 psi | 90% | 3297 fps | 99.6% |
| Accurate 3100 | <<locked>> | 94% | 57,377 psi | 90% | 3360 fps | 100% |
| Accurate 4350 | <<locked>> | 84% | 54,346 psi | 85% | 3340 fps | 100% |
| Accurate MAGPRO | <<locked>> | 94% | 56,971 psi | 89% | 3465 fps | 97.1% |
| ADI AR 2209 | <<locked>> | 90% | 55,535 psi | 87% | 3402 fps | 99.1% |
| ADI AR 2213 | <<locked>> | 94% | 57,261 psi | 90% | 3468 fps | 98.6% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 51,474 psi | 81% | 3343 fps | 98% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 46,180 psi | 72% | 3294 fps | 99.4% |
| Alliant Reloder-16 | <<locked>> | 86% | 55,448 psi | 87% | 3409 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 82% | 56,492 psi | 89% | 3419 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 90% | 54,998 psi | 86% | 3386 fps | 99% |
| Alliant Reloder-22 | <<locked>> | 94% | 57,406 psi | 90% | 3465 fps | 99.4% |
| Alliant Reloder-23 | <<locked>> | 94% | 54,737 psi | 86% | 3373 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 98% | 54,520 psi | 85% | 3435 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 90% | 55,317 psi | 87% | 3465 fps | 100% |
| Bofors RP15 | <<locked>> | 96% | 56,275 psi | 88% | 3442 fps | 99.2% |
| Bofors RP30ᴾ | <<locked>> | 100% | 54,230 psi | 85% | 3425 fps | 98.6% |
| Bofors RP5 | <<locked>> | 94% | 57,406 psi | 90% | 3465 fps | 99.4% |
| Bofors RP7 | <<locked>> | 84% | 56,507 psi | 89% | 3340 fps | 99.6% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 52,953 psi | 83% | 3376 fps | 98.7% |
| Hodgdon H414 | <<locked>> | 82% | 57,029 psi | 89% | 3415 fps | 99.9% |
| Hodgdon H4350 | <<locked>> | 86% | 57,043 psi | 89% | 3389 fps | 99.4% |
| Hodgdon H4831 | <<locked>> | 96% | 56,362 psi | 88% | 3386 fps | 97.9% |
| Hodgdon H4831 SC | <<locked>> | 92% | 55,796 psi | 87% | 3376 fps | 97.8% |
| Hodgdon Hybrid 100V | <<locked>> | 88% | 55,782 psi | 87% | 3320 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 57,159 psi | 90% | 3583 fps | 99.9% |
| Hodgdon Superformance | <<locked>> | 84% | 56,956 psi | 89% | 3438 fps | 99.8% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,014 psi | 58% | 2182 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 57,566 psi | 90% | 3333 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 82% | 55,970 psi | 88% | 3317 fps | 99.8% |
| IMR 4350 | <<locked>> | 86% | 54,897 psi | 86% | 3323 fps | 99.5% |
| IMR 4451 Enduron | <<locked>> | 82% | 54,491 psi | 85% | 3307 fps | 99.6% |
| IMR 4831 | <<locked>> | 90% | 56,159 psi | 88% | 3353 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 57,740 psi | 90% | 3379 fps | 98.3% |
| IMR 7828 SSC | <<locked>> | 92% | 55,274 psi | 87% | 3445 fps | 98.4% |
| Lovex S065 | <<locked>> | 84% | 55,172 psi | 86% | 3307 fps | 100% |
| Lovex S070 | <<locked>> | 86% | 56,942 psi | 89% | 3360 fps | 99.9% |
| Lovex S071 | <<locked>> | 98% | 54,998 psi | 86% | 3320 fps | 100% |
| Norma 204 | <<locked>> | 86% | 55,796 psi | 87% | 3379 fps | 99% |
| Norma 217ᴾ | <<locked>> | 100% | 41,829 psi | 66% | 3209 fps | 97.8% |
| Norma MRP | <<locked>> | 92% | 57,435 psi | 90% | 3488 fps | 99.9% |
| Norma URP | <<locked>> | 86% | 56,463 psi | 88% | 3383 fps | 100% |
| Ramshot Grand | <<locked>> | 90% | 55,100 psi | 86% | 3448 fps | 98.7% |
| Ramshot Hunter | <<locked>> | 86% | 55,405 psi | 87% | 3383 fps | 100% |
| Ramshot Magnum | <<locked>> | 94% | 56,637 psi | 89% | 3419 fps | 99.8% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,884 psi | 59% | 2234 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 84% | 54,679 psi | 86% | 3363 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 86% | 56,971 psi | 89% | 3458 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 98% | 54,375 psi | 85% | 3504 fps | 100% |
| ReloadSwiss RS 80ᴾ | <<locked>> | 100% | 53,548 psi | 84% | 3442 fps | 97.3% |
| Rottweil R 904 | <<locked>> | 90% | 56,521 psi | 89% | 3366 fps | 98.5% |
| Rottweil R 905 | <<locked>> | 90% | 54,476 psi | 85% | 3369 fps | 99.1% |
| Rottweil R 907 | <<locked>> | 84% | 56,507 psi | 89% | 3340 fps | 99.6% |
| Shooters World Long Rifle | <<locked>> | 84% | 55,172 psi | 86% | 3307 fps | 100% |
| Shooters World SW4350 | <<locked>> | 86% | 56,942 psi | 89% | 3360 fps | 99.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 57,334 psi | 90% | 3196 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 54,447 psi | 85% | 3251 fps | 99.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 90% | 54,056 psi | 85% | 3366 fps | 99% |
| Somchem S355 | <<locked>> | 82% | 57,522 psi | 90% | 3337 fps | 100% |
| Somchem S361 | <<locked>> | 88% | 54,491 psi | 85% | 3284 fps | 97.5% |
| Somchem S365 | <<locked>> | 88% | 57,217 psi | 90% | 3383 fps | 100% |
| Somchem S385 | <<locked>> | 90% | 55,056 psi | 86% | 3340 fps | 99.5% |
| Unknown powder | <<locked>> | 84% | 56,463 psi | 88% | 3383 fps | 100% |
| Vihtavuori N150 | <<locked>> | 86% | 56,101 psi | 88% | 3264 fps | 100% |
| Vihtavuori N160 | <<locked>> | 84% | 56,927 psi | 89% | 3346 fps | 100% |
| Vihtavuori N165 | <<locked>> | 96% | 56,492 psi | 89% | 3350 fps | 99.5% |
| Vihtavuori N550 | <<locked>> | 84% | 57,667 psi | 90% | 3399 fps | 100% |
| Vihtavuori N555 | <<locked>> | 92% | 57,087 psi | 89% | 3406 fps | 100% |
| Vihtavuori N560 | <<locked>> | 94% | 57,609 psi | 90% | 3491 fps | 98.3% |
| Vihtavuori N565 | <<locked>> | 98% | 57,276 psi | 90% | 3455 fps | 98.5% |
| Vihtavuori N568ᴾ | <<locked>> | 100% | 54,302 psi | 85% | 3445 fps | 96.9% |
| Winchester 6.5 StaBALL | <<locked>> | 84% | 54,259 psi | 85% | 3261 fps | 100% |
| Winchester 760 | <<locked>> | 82% | 57,029 psi | 89% | 3415 fps | 99.9% |
| Winchester StaBALL HD | <<locked>> | 96% | 57,290 psi | 90% | 3524 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 56,637 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 2700 | <<locked>> | 80% | 53,490 psi | 84% | 3235 fps | 99.3% |
| Accurate 3100 | <<locked>> | 80% | 35,433 psi | 56% | 2907 fps | 96.8% |
| Accurate 4350 | <<locked>> | 80% | 47,326 psi | 74% | 3212 fps | 100% |
| Accurate MAGPRO | <<locked>> | 90% | 49,342 psi | 77% | 3314 fps | 95.2% |
| ADI AR 2209 | <<locked>> | 80% | 39,407 psi | 62% | 3054 fps | 95.3% |
| ADI AR 2213 | <<locked>> | 86% | 43,366 psi | 68% | 3179 fps | 95.3% |
| ADI AR 2217 | <<locked>> | 94% | 41,989 psi | 66% | 3130 fps | 95.2% |
| ADI AR 2225 | <<locked>> | 92% | 35,259 psi | 55% | 3005 fps | 95.9% |
| Alliant Reloder-16 | <<locked>> | 80% | 45,208 psi | 71% | 3215 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 80% | 52,692 psi | 83% | 3356 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 39,421 psi | 62% | 3048 fps | 95.4% |
| Alliant Reloder-22 | <<locked>> | 84% | 40,640 psi | 64% | 3117 fps | 96% |
| Alliant Reloder-23 | <<locked>> | 80% | 34,055 psi | 53% | 2943 fps | 99.3% |
| Alliant Reloder-25 | <<locked>> | 82% | 31,691 psi | 50% | 2894 fps | 96% |
| Alliant Reloder-26 | <<locked>> | 80% | 37,594 psi | 59% | 3097 fps | 98.8% |
| Bofors RP15 | <<locked>> | 86% | 40,306 psi | 63% | 3107 fps | 95.7% |
| Bofors RP30 | <<locked>> | 92% | 41,075 psi | 64% | 3146 fps | 95.3% |
| Bofors RP5 | <<locked>> | 84% | 40,640 psi | 64% | 3117 fps | 96% |
| Bofors RP7 | <<locked>> | 80% | 49,879 psi | 78% | 3219 fps | 98.9% |
| Hodgdon H1000 | <<locked>> | 92% | 40,147 psi | 63% | 3091 fps | 95.2% |
| Hodgdon H414 | <<locked>> | 80% | 53,287 psi | 84% | 3346 fps | 99.6% |
| Hodgdon H4350 | <<locked>> | 80% | 47,268 psi | 74% | 3199 fps | 97.9% |
| Hodgdon H4831 | <<locked>> | 90% | 46,325 psi | 73% | 3186 fps | 95.5% |
| Hodgdon H4831 SC | <<locked>> | 86% | 45,455 psi | 71% | 3169 fps | 95.3% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 42,627 psi | 67% | 3081 fps | 100% |
| Hodgdon Retumbo | 64.4 gr | 88% | 37,826 psi | 59% | 3130 fps | 95.6% |
| Hodgdon Superformance | <<locked>> | 80% | 49,052 psi | 77% | 3291 fps | 99% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,702 psi | 43% | 1959 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 54,041 psi | 85% | 3274 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 80% | 52,634 psi | 82% | 3255 fps | 99.5% |
| IMR 4350 | <<locked>> | 80% | 45,165 psi | 71% | 3130 fps | 98.1% |
| IMR 4451 Enduron | <<locked>> | 80% | 51,024 psi | 80% | 3241 fps | 99.3% |
| IMR 4831 | <<locked>> | 80% | 40,886 psi | 64% | 3054 fps | 99.4% |
| IMR 4955 Enduron | <<locked>> | 84% | 44,686 psi | 70% | 3120 fps | 95.3% |
| IMR 7828 SSC | 64.3 gr | 86% | 44,599 psi | 70% | 3222 fps | 95.8% |
| Lovex S065 | <<locked>> | 80% | 48,762 psi | 76% | 3189 fps | 99.7% |
| Lovex S070 | <<locked>> | 80% | 47,050 psi | 74% | 3173 fps | 99% |
| Lovex S071 | <<locked>> | 82% | 32,503 psi | 51% | 2825 fps | 95.6% |
| Norma 204 | <<locked>> | 80% | 45,368 psi | 71% | 3173 fps | 97% |
| Norma 217 | <<locked>> | 96% | 36,332 psi | 57% | 3061 fps | 95.7% |
| Norma MRP | <<locked>> | 80% | 37,173 psi | 58% | 3054 fps | 96.2% |
| Norma URP | <<locked>> | 80% | 46,354 psi | 73% | 3196 fps | 99.9% |
| Ramshot Grand | <<locked>> | 84% | 43,671 psi | 68% | 3209 fps | 95.9% |
| Ramshot Hunter | <<locked>> | 80% | 45,223 psi | 71% | 3186 fps | 99.1% |
| Ramshot Magnum | <<locked>> | 84% | 38,189 psi | 60% | 3041 fps | 96.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,369 psi | 44% | 2005 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 47,398 psi | 74% | 3232 fps | 99.9% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 45,600 psi | 71% | 3248 fps | 99.8% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 34,795 psi | 55% | 3025 fps | 95.5% |
| ReloadSwiss RS 80 | <<locked>> | 96% | 45,672 psi | 72% | 3278 fps | 95.1% |
| Rottweil R 904 | <<locked>> | 82% | 43,453 psi | 68% | 3100 fps | 95.5% |
| Rottweil R 905 | <<locked>> | 80% | 38,827 psi | 61% | 3035 fps | 95.4% |
| Rottweil R 907 | <<locked>> | 80% | 49,879 psi | 78% | 3219 fps | 98.9% |
| Shooters World Long Rifle | <<locked>> | 80% | 48,762 psi | 76% | 3189 fps | 99.7% |
| Shooters World SW4350 | <<locked>> | 80% | 47,050 psi | 74% | 3173 fps | 99% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 54,041 psi | 85% | 3150 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 47,761 psi | 75% | 3127 fps | 99% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 38,493 psi | 60% | 3028 fps | 95.2% |
| Somchem S355 | <<locked>> | 80% | 54,056 psi | 85% | 3281 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 44,585 psi | 70% | 3087 fps | 95% |
| Somchem S365 | <<locked>> | 80% | 43,424 psi | 68% | 3143 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 39,508 psi | 62% | 3018 fps | 96.6% |
| Unknown powder | <<locked>> | 80% | 49,472 psi | 78% | 3255 fps | 99.9% |
| Vihtavuori N150 | <<locked>> | 80% | 46,369 psi | 73% | 3100 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 49,719 psi | 78% | 3222 fps | 100% |
| Vihtavuori N165 | <<locked>> | 84% | 37,985 psi | 60% | 2966 fps | 95.7% |
| Vihtavuori N550 | <<locked>> | 80% | 50,444 psi | 79% | 3274 fps | 100% |
| Vihtavuori N555 | <<locked>> | 80% | 38,174 psi | 60% | 3031 fps | 99.3% |
| Vihtavuori N560 | <<locked>> | 88% | 46,978 psi | 74% | 3281 fps | 95.9% |
| Vihtavuori N565 | <<locked>> | 90% | 43,381 psi | 68% | 3173 fps | 95.2% |
| Vihtavuori N568 | <<locked>> | 98% | 50,299 psi | 79% | 3369 fps | 95.9% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 47,195 psi | 74% | 3140 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 53,287 psi | 84% | 3346 fps | 99.6% |
| Winchester StaBALL HD | 60.1 gr | 80% | 30,313 psi | 48% | 2949 fps | 99.5% |
| Winchester Supreme 780 | <<locked>> | 80% | 39,349 psi | 62% | 3009 fps | 95.5% |
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 81 powders for .257 Weath. Mag. loaded with the .257 | 100gr | Sierra GameKing. Hodgdon Retumbo delivers the highest muzzle velocity at 3,583 fps; across all powders the maximum-charge window runs from 2,182 fps to 3,583 fps. ADI AR 2217 gives the best case fill at 100 %, and 81 of the 81 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 1:11.5 twist; slower twists will usually not stabilise this weight. ADI AR 2217, ADI AR 2225, Alliant Reloder-33 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, IMR 7828 SSC, Hodgdon Retumbo rank at the top here: for .257 Weath. Mag. with the .257 | 100gr | Sierra GameKing they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Alliant Reloder-33, IMR 7977 Enduron, Vihtavuori N170 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.