Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 100gr | Nosler Expansion Tip bullet and 77 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-25, Winchester StaBALL HD and Alliant Reloder-26.
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% | 54,215 psi | 85% | 3310 fps | 99.9% |
| Accurate 4350 | <<locked>> | 86% | 55,274 psi | 87% | 3356 fps | 100% |
| Accurate High Country | <<locked>> | 92% | 55,927 psi | 88% | 3474 fps | 98.4% |
| Accurate MAGPRO | <<locked>> | 94% | 57,145 psi | 90% | 3478 fps | 97.6% |
| ADI AR 2208 | <<locked>> | 82% | 56,275 psi | 88% | 3320 fps | 100% |
| ADI AR 2209 | <<locked>> | 92% | 56,579 psi | 89% | 3419 fps | 99.1% |
| ADI AR 2213 | <<locked>> | 94% | 54,389 psi | 85% | 3415 fps | 98% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 48,863 psi | 77% | 3291 fps | 97.2% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 43,352 psi | 68% | 3232 fps | 98.7% |
| Alliant Power Pro Varmint | <<locked>> | 92% | 56,884 psi | 89% | 3419 fps | 99.2% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 57,667 psi | 90% | 3350 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 88% | 56,478 psi | 89% | 3428 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 82% | 53,708 psi | 84% | 3376 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 92% | 56,173 psi | 88% | 3406 fps | 99.1% |
| Alliant Reloder-22 | <<locked>> | 94% | 54,302 psi | 85% | 3412 fps | 99% |
| Alliant Reloder-23 | <<locked>> | 96% | 55,448 psi | 87% | 3386 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 54,897 psi | 86% | 3448 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 92% | 56,275 psi | 88% | 3484 fps | 100% |
| Bofors RP15 | <<locked>> | 98% | 57,217 psi | 90% | 3461 fps | 99.3% |
| Bofors RP30ᴾ | <<locked>> | 100% | 50,821 psi | 80% | 3366 fps | 97.9% |
| Bofors RP5 | <<locked>> | 94% | 54,302 psi | 85% | 3412 fps | 99% |
| Bofors RP7 | <<locked>> | 84% | 54,259 psi | 85% | 3301 fps | 99.4% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 53,911 psi | 84% | 3396 fps | 98.8% |
| Hodgdon H414 | <<locked>> | 86% | 57,305 psi | 90% | 3419 fps | 99.8% |
| Hodgdon H4350 | <<locked>> | 84% | 56,130 psi | 88% | 3373 fps | 99.2% |
| Hodgdon H4831 | <<locked>> | 92% | 54,288 psi | 85% | 3346 fps | 97.3% |
| Hodgdon H4831 SC | <<locked>> | 94% | 57,000 psi | 89% | 3396 fps | 97.9% |
| Hodgdon Hybrid 100V | <<locked>> | 90% | 56,536 psi | 89% | 3333 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 53,853 psi | 84% | 3520 fps | 99.7% |
| Hodgdon Superformance | <<locked>> | 84% | 54,172 psi | 85% | 3389 fps | 99.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,738 psi | 58% | 2169 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 56,057 psi | 88% | 3346 fps | 99.6% |
| IMR 4451 Enduron | <<locked>> | 84% | 55,883 psi | 88% | 3330 fps | 99.7% |
| IMR 4831 | <<locked>> | 88% | 55,753 psi | 87% | 3346 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 55,361 psi | 87% | 3333 fps | 97.7% |
| IMR 7828 SSC | <<locked>> | 96% | 56,057 psi | 88% | 3458 fps | 98.4% |
| Lovex S065 | <<locked>> | 86% | 56,347 psi | 88% | 3327 fps | 100% |
| Lovex S070 | <<locked>> | 86% | 54,360 psi | 85% | 3317 fps | 99.7% |
| Lovex S071ᴾ | <<locked>> | 100% | 55,303 psi | 87% | 3327 fps | 100% |
| Norma 204 | <<locked>> | 88% | 57,072 psi | 89% | 3402 fps | 99.1% |
| Norma 217ᴾ | <<locked>> | 100% | 38,856 psi | 61% | 3136 fps | 96.7% |
| Norma MRP | <<locked>> | 92% | 54,172 psi | 85% | 3435 fps | 99.7% |
| Norma URP | <<locked>> | 88% | 57,479 psi | 90% | 3399 fps | 100% |
| Ramshot Grand | <<locked>> | 96% | 57,058 psi | 89% | 3484 fps | 98.8% |
| Ramshot Hunter | <<locked>> | 88% | 56,507 psi | 89% | 3402 fps | 100% |
| Ramshot Magnum | <<locked>> | 98% | 55,506 psi | 87% | 3402 fps | 99.6% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,579 psi | 59% | 2221 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 82% | 57,305 psi | 90% | 3428 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 55,535 psi | 87% | 3379 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 86% | 54,099 psi | 85% | 3412 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 54,926 psi | 86% | 3517 fps | 100% |
| ReloadSwiss RS 80ᴾ | <<locked>> | 100% | 49,893 psi | 78% | 3373 fps | 96.3% |
| Rottweil R 903 | <<locked>> | 82% | 55,230 psi | 87% | 3304 fps | 100% |
| Rottweil R 904 | <<locked>> | 92% | 57,638 psi | 90% | 3383 fps | 98.5% |
| Rottweil R 905 | <<locked>> | 92% | 55,564 psi | 87% | 3392 fps | 99.1% |
| Rottweil R 907 | <<locked>> | 84% | 54,259 psi | 85% | 3301 fps | 99.4% |
| Shooters World Long Rifle | <<locked>> | 86% | 56,347 psi | 88% | 3327 fps | 100% |
| Shooters World SW4350 | <<locked>> | 86% | 54,360 psi | 85% | 3317 fps | 99.7% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 57,014 psi | 89% | 3369 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 55,347 psi | 87% | 3169 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 55,579 psi | 87% | 3271 fps | 99.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 92% | 55,114 psi | 86% | 3386 fps | 99% |
| Somchem S355 | <<locked>> | 82% | 55,042 psi | 86% | 3301 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 55,767 psi | 87% | 3304 fps | 97.6% |
| Somchem S365 | <<locked>> | 88% | 54,346 psi | 85% | 3343 fps | 100% |
| Somchem S385 | <<locked>> | 92% | 56,014 psi | 88% | 3360 fps | 99.6% |
| Vihtavuori N150 | <<locked>> | 84% | 56,347 psi | 88% | 3264 fps | 100% |
| Vihtavuori N160 | <<locked>> | 86% | 55,724 psi | 87% | 3333 fps | 100% |
| Vihtavuori N165 | <<locked>> | 96% | 55,695 psi | 87% | 3333 fps | 99.4% |
| Vihtavuori N550 | <<locked>> | 86% | 54,853 psi | 86% | 3333 fps | 100% |
| Vihtavuori N555 | <<locked>> | 94% | 57,609 psi | 90% | 3419 fps | 100% |
| Vihtavuori N560 | <<locked>> | 92% | 54,056 psi | 85% | 3425 fps | 97.5% |
| Vihtavuori N565 | <<locked>> | 98% | 53,882 psi | 84% | 3396 fps | 97.8% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 55,448 psi | 87% | 3281 fps | 100% |
| Winchester 760 | <<locked>> | 86% | 57,580 psi | 90% | 3425 fps | 99.9% |
| Winchester StaBALL HD | <<locked>> | 98% | 57,696 psi | 90% | 3537 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 94% | 56,173 psi | 88% | 3353 fps | 99.1% |
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% | 32,895 psi | 52% | 2841 fps | 95.7% |
| Accurate 4350 | <<locked>> | 80% | 44,541 psi | 70% | 3156 fps | 99.7% |
| Accurate High Country | <<locked>> | 86% | 44,875 psi | 70% | 3248 fps | 95.9% |
| Accurate MAGPRO | <<locked>> | 90% | 49,356 psi | 77% | 3330 fps | 95.8% |
| ADI AR 2208 | <<locked>> | 80% | 52,997 psi | 83% | 3264 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 39,987 psi | 63% | 3074 fps | 95.4% |
| ADI AR 2213 | <<locked>> | 88% | 44,048 psi | 69% | 3196 fps | 95.3% |
| ADI AR 2217 | <<locked>> | 96% | 42,511 psi | 67% | 3143 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 94% | 35,317 psi | 55% | 3012 fps | 95.8% |
| Alliant Power Pro Varmint | <<locked>> | 82% | 40,321 psi | 63% | 3071 fps | 95.5% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 54,041 psi | 85% | 3287 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 80% | 42,844 psi | 67% | 3169 fps | 99.8% |
| Alliant Reloder-17 | <<locked>> | 80% | 49,908 psi | 78% | 3310 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 39,943 psi | 63% | 3064 fps | 95.4% |
| Alliant Reloder-22 | <<locked>> | 86% | 41,147 psi | 64% | 3130 fps | 96% |
| Alliant Reloder-23 | <<locked>> | 80% | 31,792 psi | 50% | 2881 fps | 98.7% |
| Alliant Reloder-25 | 59.3 gr | 84% | 31,633 psi | 50% | 2897 fps | 95.8% |
| Alliant Reloder-26 | 61.1 gr | 80% | 34,925 psi | 55% | 3028 fps | 97.9% |
| Bofors RP15 | <<locked>> | 88% | 40,596 psi | 64% | 3114 fps | 95.6% |
| Bofors RP30 | <<locked>> | 94% | 41,118 psi | 64% | 3153 fps | 95.2% |
| Bofors RP5 | <<locked>> | 86% | 41,147 psi | 64% | 3130 fps | 96% |
| Bofors RP7 | <<locked>> | 80% | 47,630 psi | 75% | 3173 fps | 98.4% |
| Hodgdon H1000 | <<locked>> | 92% | 40,582 psi | 64% | 3100 fps | 95.1% |
| Hodgdon H414 | <<locked>> | 80% | 46,572 psi | 73% | 3215 fps | 98.7% |
| Hodgdon H4350 | <<locked>> | 80% | 49,081 psi | 77% | 3235 fps | 98.1% |
| Hodgdon H4831 | <<locked>> | 88% | 47,166 psi | 74% | 3209 fps | 95.6% |
| Hodgdon H4831 SC | <<locked>> | 88% | 46,253 psi | 72% | 3189 fps | 95.3% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 40,408 psi | 63% | 3038 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 90% | 38,058 psi | 60% | 3136 fps | 95.4% |
| Hodgdon Superformance | <<locked>> | 80% | 46,369 psi | 73% | 3238 fps | 98.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,398 psi | 43% | 1946 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 43,091 psi | 68% | 3087 fps | 97.5% |
| IMR 4451 Enduron | <<locked>> | 80% | 48,994 psi | 77% | 3202 fps | 99% |
| IMR 4831 | <<locked>> | 80% | 42,627 psi | 67% | 3097 fps | 99.6% |
| IMR 4955 Enduron | <<locked>> | 86% | 45,629 psi | 72% | 3140 fps | 95.4% |
| IMR 7828 SSC | <<locked>> | 90% | 45,295 psi | 71% | 3238 fps | 95.8% |
| Lovex S065 | <<locked>> | 80% | 46,485 psi | 73% | 3143 fps | 99.4% |
| Lovex S070 | <<locked>> | 80% | 44,715 psi | 70% | 3123 fps | 98.5% |
| Lovex S071 | <<locked>> | 84% | 32,242 psi | 51% | 2822 fps | 95.4% |
| Norma 204 | <<locked>> | 80% | 43,207 psi | 68% | 3123 fps | 96.3% |
| Norma 217 | <<locked>> | 98% | 36,216 psi | 57% | 3064 fps | 95.5% |
| Norma MRP | <<locked>> | 80% | 34,693 psi | 54% | 2992 fps | 95% |
| Norma URP | <<locked>> | 80% | 43,947 psi | 69% | 3146 fps | 99.7% |
| Ramshot Grand | <<locked>> | 88% | 42,105 psi | 66% | 3173 fps | 95.2% |
| Ramshot Hunter | <<locked>> | 80% | 42,975 psi | 67% | 3136 fps | 98.6% |
| Ramshot Magnum | <<locked>> | 88% | 37,565 psi | 59% | 3028 fps | 95.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,021 psi | 44% | 1991 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 53,127 psi | 83% | 3363 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 44,686 psi | 70% | 3176 fps | 99.7% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 43,105 psi | 68% | 3196 fps | 99.5% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 34,940 psi | 55% | 3031 fps | 95.3% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 45,890 psi | 72% | 3287 fps | 95% |
| Rottweil R 903 | <<locked>> | 80% | 51,663 psi | 81% | 3245 fps | 100% |
| Rottweil R 904 | <<locked>> | 84% | 44,237 psi | 69% | 3120 fps | 95.6% |
| Rottweil R 905 | <<locked>> | 82% | 39,218 psi | 61% | 3048 fps | 95.4% |
| Rottweil R 907 | <<locked>> | 80% | 47,630 psi | 75% | 3173 fps | 98.4% |
| Shooters World Long Rifle | <<locked>> | 80% | 46,485 psi | 73% | 3143 fps | 99.4% |
| Shooters World SW4350 | <<locked>> | 80% | 44,715 psi | 70% | 3123 fps | 98.5% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 53,432 psi | 84% | 3310 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 51,822 psi | 81% | 3117 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 45,600 psi | 71% | 3084 fps | 98.6% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 38,870 psi | 61% | 3038 fps | 95.2% |
| Somchem S355 | <<locked>> | 80% | 51,561 psi | 81% | 3241 fps | 100% |
| Somchem S361 | <<locked>> | 84% | 45,455 psi | 71% | 3104 fps | 95.1% |
| Somchem S365 | <<locked>> | 80% | 40,828 psi | 64% | 3094 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 37,028 psi | 58% | 2956 fps | 95.5% |
| Vihtavuori N150 | <<locked>> | 80% | 49,385 psi | 77% | 3153 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 45,382 psi | 71% | 3143 fps | 99.8% |
| Vihtavuori N165 | <<locked>> | 84% | 36,927 psi | 58% | 2943 fps | 95.1% |
| Vihtavuori N550 | <<locked>> | 80% | 44,904 psi | 70% | 3146 fps | 99.7% |
| Vihtavuori N555 | <<locked>> | 80% | 35,563 psi | 56% | 2969 fps | 98.6% |
| Vihtavuori N560 | <<locked>> | 88% | 46,731 psi | 73% | 3274 fps | 95.7% |
| Vihtavuori N565 | <<locked>> | 92% | 43,468 psi | 68% | 3176 fps | 95% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 44,875 psi | 70% | 3100 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 46,775 psi | 73% | 3222 fps | 98.7% |
| Winchester StaBALL HD | 58.7 gr | 80% | 28,181 psi | 44% | 2874 fps | 98.5% |
| Winchester Supreme 780 | <<locked>> | 84% | 39,146 psi | 61% | 3005 fps | 95.2% |
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 77 powders for .257 Weath. Mag. loaded with the .257 | 100gr | Nosler Expansion Tip. Winchester StaBALL HD delivers the highest muzzle velocity at 3,537 fps; across all powders the maximum-charge window runs from 2,169 fps to 3,537 fps. ADI AR 2217 gives the best case fill at 100 %, and 77 of the 77 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. Alliant Reloder-25, Winchester StaBALL HD, Alliant Reloder-26 rank at the top here: for .257 Weath. Mag. with the .257 | 100gr | Nosler Expansion Tip 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.