Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 100gr | Osprey Virtus 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, 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% | 54,128 psi | 85% | 3307 fps | 99.9% |
| Accurate 4350 | <<locked>> | 86% | 55,143 psi | 86% | 3353 fps | 100% |
| Accurate MAGPRO | <<locked>> | 94% | 57,000 psi | 89% | 3474 fps | 97.6% |
| ADI AR 2208 | <<locked>> | 82% | 56,449 psi | 88% | 3323 fps | 100% |
| ADI AR 2209 | <<locked>> | 92% | 56,768 psi | 89% | 3425 fps | 99.1% |
| ADI AR 2213 | <<locked>> | 94% | 54,563 psi | 86% | 3419 fps | 98% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 48,776 psi | 76% | 3287 fps | 97.2% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 43,497 psi | 68% | 3235 fps | 98.8% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 57,595 psi | 90% | 3346 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 88% | 56,362 psi | 88% | 3425 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 84% | 57,711 psi | 90% | 3438 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 92% | 56,057 psi | 88% | 3406 fps | 99.1% |
| Alliant Reloder-22 | <<locked>> | 94% | 54,476 psi | 85% | 3412 fps | 99% |
| Alliant Reloder-23 | <<locked>> | 96% | 55,608 psi | 87% | 3386 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 55,085 psi | 86% | 3451 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 92% | 56,188 psi | 88% | 3481 fps | 100% |
| Bofors RP15 | <<locked>> | 98% | 57,116 psi | 90% | 3458 fps | 99.2% |
| Bofors RP30ᴾ | <<locked>> | 100% | 50,995 psi | 80% | 3366 fps | 97.9% |
| Bofors RP5 | <<locked>> | 94% | 54,476 psi | 85% | 3412 fps | 99% |
| Bofors RP7 | <<locked>> | 84% | 54,201 psi | 85% | 3301 fps | 99.3% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 54,085 psi | 85% | 3396 fps | 98.8% |
| Hodgdon H414 | <<locked>> | 86% | 57,232 psi | 90% | 3419 fps | 99.8% |
| Hodgdon H4350 | <<locked>> | 84% | 56,304 psi | 88% | 3373 fps | 99.2% |
| Hodgdon H4831 | <<locked>> | 92% | 54,215 psi | 85% | 3343 fps | 97.3% |
| Hodgdon H4831 SC | <<locked>> | 94% | 57,159 psi | 90% | 3396 fps | 97.9% |
| Hodgdon Hybrid 100V | <<locked>> | 90% | 56,710 psi | 89% | 3337 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 53,998 psi | 85% | 3524 fps | 99.7% |
| Hodgdon Superformance | <<locked>> | 84% | 54,099 psi | 85% | 3389 fps | 99.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,912 psi | 58% | 2175 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 55,985 psi | 88% | 3340 fps | 99.6% |
| IMR 4451 Enduron | <<locked>> | 84% | 55,825 psi | 87% | 3330 fps | 99.7% |
| IMR 4831 | <<locked>> | 88% | 55,898 psi | 88% | 3350 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 55,506 psi | 87% | 3337 fps | 97.7% |
| IMR 7828 SSC | <<locked>> | 96% | 56,231 psi | 88% | 3461 fps | 98.4% |
| Lovex S065 | <<locked>> | 86% | 56,260 psi | 88% | 3323 fps | 100% |
| Lovex S070 | <<locked>> | 86% | 54,505 psi | 85% | 3320 fps | 99.7% |
| Lovex S071ᴾ | <<locked>> | 100% | 55,216 psi | 87% | 3323 fps | 100% |
| Norma 204 | <<locked>> | 88% | 57,246 psi | 90% | 3406 fps | 99.1% |
| Norma 217ᴾ | <<locked>> | 100% | 38,783 psi | 61% | 3133 fps | 96.6% |
| Norma MRP | <<locked>> | 92% | 54,360 psi | 85% | 3435 fps | 99.7% |
| Norma URP | <<locked>> | 88% | 57,653 psi | 90% | 3402 fps | 100% |
| Ramshot Grand | <<locked>> | 96% | 56,971 psi | 89% | 3481 fps | 98.8% |
| Ramshot Hunter | <<locked>> | 88% | 56,652 psi | 89% | 3406 fps | 100% |
| Ramshot Magnum | <<locked>> | 98% | 55,405 psi | 87% | 3399 fps | 99.6% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,536 psi | 59% | 2221 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 82% | 57,493 psi | 90% | 3428 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 55,695 psi | 87% | 3383 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 86% | 53,998 psi | 85% | 3409 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 55,100 psi | 86% | 3520 fps | 100% |
| ReloadSwiss RS 80ᴾ | <<locked>> | 100% | 49,792 psi | 78% | 3373 fps | 96.3% |
| Rottweil R 903 | <<locked>> | 82% | 55,419 psi | 87% | 3307 fps | 100% |
| Rottweil R 904 | <<locked>> | 90% | 54,128 psi | 85% | 3320 fps | 97.9% |
| Rottweil R 905 | <<locked>> | 92% | 55,463 psi | 87% | 3389 fps | 99.1% |
| Rottweil R 907 | <<locked>> | 84% | 54,201 psi | 85% | 3301 fps | 99.3% |
| Shooters World Long Rifle | <<locked>> | 86% | 56,260 psi | 88% | 3323 fps | 100% |
| Shooters World SW4350 | <<locked>> | 86% | 54,505 psi | 85% | 3320 fps | 99.7% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 57,174 psi | 90% | 3373 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 55,245 psi | 87% | 3169 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 55,709 psi | 87% | 3271 fps | 99.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 92% | 55,027 psi | 86% | 3386 fps | 99% |
| Somchem S355 | <<locked>> | 82% | 54,955 psi | 86% | 3297 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 55,898 psi | 88% | 3307 fps | 97.6% |
| Somchem S365 | <<locked>> | 88% | 54,230 psi | 85% | 3340 fps | 100% |
| Somchem S385 | <<locked>> | 92% | 55,941 psi | 88% | 3360 fps | 99.6% |
| Vihtavuori N150 | <<locked>> | 84% | 56,521 psi | 89% | 3268 fps | 100% |
| Vihtavuori N160 | <<locked>> | 86% | 55,622 psi | 87% | 3330 fps | 100% |
| Vihtavuori N165 | <<locked>> | 96% | 55,840 psi | 88% | 3337 fps | 99.4% |
| Vihtavuori N550 | <<locked>> | 86% | 55,027 psi | 86% | 3337 fps | 100% |
| Vihtavuori N555 | <<locked>> | 94% | 57,508 psi | 90% | 3415 fps | 100% |
| Vihtavuori N560 | <<locked>> | 92% | 54,201 psi | 85% | 3428 fps | 97.6% |
| Vihtavuori N565 | <<locked>> | 98% | 54,041 psi | 85% | 3399 fps | 97.8% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 55,593 psi | 87% | 3281 fps | 100% |
| Winchester 760 | <<locked>> | 86% | 57,493 psi | 90% | 3422 fps | 99.9% |
| Winchester StaBALL HD | <<locked>> | 98% | 57,580 psi | 90% | 3537 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 94% | 56,333 psi | 88% | 3356 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% | 33,025 psi | 52% | 2844 fps | 95.7% |
| Accurate 4350 | <<locked>> | 80% | 44,730 psi | 70% | 3159 fps | 99.8% |
| Accurate MAGPRO | <<locked>> | 90% | 49,284 psi | 77% | 3327 fps | 95.8% |
| ADI AR 2208 | <<locked>> | 80% | 52,910 psi | 83% | 3264 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 40,118 psi | 63% | 3074 fps | 95.4% |
| ADI AR 2213 | <<locked>> | 88% | 43,976 psi | 69% | 3196 fps | 95.3% |
| ADI AR 2217 | <<locked>> | 96% | 42,453 psi | 67% | 3143 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 94% | 35,418 psi | 56% | 3012 fps | 95.8% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 54,230 psi | 85% | 3291 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 80% | 42,975 psi | 67% | 3169 fps | 99.8% |
| Alliant Reloder-17 | <<locked>> | 80% | 50,067 psi | 78% | 3310 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 40,059 psi | 63% | 3068 fps | 95.5% |
| Alliant Reloder-22 | <<locked>> | 86% | 41,060 psi | 64% | 3130 fps | 96% |
| Alliant Reloder-23 | <<locked>> | 80% | 31,720 psi | 50% | 2877 fps | 98.7% |
| Alliant Reloder-25 | <<locked>> | 84% | 31,749 psi | 50% | 2900 fps | 95.8% |
| Alliant Reloder-26 | <<locked>> | 80% | 34,867 psi | 55% | 3028 fps | 97.9% |
| Bofors RP15 | <<locked>> | 88% | 40,712 psi | 64% | 3117 fps | 95.7% |
| Bofors RP30 | <<locked>> | 94% | 41,046 psi | 64% | 3150 fps | 95.1% |
| Bofors RP5 | <<locked>> | 86% | 41,060 psi | 64% | 3130 fps | 96% |
| Bofors RP7 | <<locked>> | 80% | 47,558 psi | 75% | 3169 fps | 98.4% |
| Hodgdon H1000 | <<locked>> | 92% | 40,698 psi | 64% | 3104 fps | 95.2% |
| Hodgdon H414 | <<locked>> | 80% | 46,702 psi | 73% | 3219 fps | 98.7% |
| Hodgdon H4350 | <<locked>> | 80% | 49,255 psi | 77% | 3241 fps | 98.2% |
| Hodgdon H4831 | <<locked>> | 88% | 47,326 psi | 74% | 3209 fps | 95.7% |
| Hodgdon H4831 SC | <<locked>> | 88% | 46,180 psi | 72% | 3186 fps | 95.3% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 40,364 psi | 63% | 3035 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 90% | 38,000 psi | 60% | 3133 fps | 95.4% |
| Hodgdon Superformance | <<locked>> | 80% | 46,514 psi | 73% | 3241 fps | 98.5% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,557 psi | 43% | 1949 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 43,221 psi | 68% | 3087 fps | 97.5% |
| IMR 4451 Enduron | <<locked>> | 80% | 49,124 psi | 77% | 3202 fps | 99% |
| IMR 4831 | <<locked>> | 80% | 42,569 psi | 67% | 3097 fps | 99.6% |
| IMR 4955 Enduron | <<locked>> | 86% | 45,585 psi | 71% | 3136 fps | 95.3% |
| IMR 7828 SSC | <<locked>> | 90% | 45,426 psi | 71% | 3241 fps | 95.9% |
| Lovex S065 | <<locked>> | 80% | 46,383 psi | 73% | 3143 fps | 99.4% |
| Lovex S070 | <<locked>> | 80% | 44,889 psi | 70% | 3127 fps | 98.5% |
| Lovex S071 | <<locked>> | 84% | 32,343 psi | 51% | 2825 fps | 95.4% |
| Norma 204 | <<locked>> | 80% | 43,134 psi | 68% | 3123 fps | 96.3% |
| Norma 217 | <<locked>> | 98% | 36,143 psi | 57% | 3061 fps | 95.5% |
| Norma MRP | 59.4 gr | 80% | 34,824 psi | 55% | 2992 fps | 95% |
| Norma URP | <<locked>> | 80% | 44,092 psi | 69% | 3150 fps | 99.7% |
| Ramshot Grand | <<locked>> | 88% | 42,032 psi | 66% | 3169 fps | 95.2% |
| Ramshot Hunter | <<locked>> | 80% | 42,917 psi | 67% | 3136 fps | 98.6% |
| Ramshot Magnum | <<locked>> | 88% | 37,507 psi | 59% | 3025 fps | 95.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,992 psi | 44% | 1991 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 53,287 psi | 84% | 3366 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 44,831 psi | 70% | 3179 fps | 99.7% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 43,265 psi | 68% | 3199 fps | 99.5% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 34,882 psi | 55% | 3028 fps | 95.3% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 46,050 psi | 72% | 3291 fps | 95.1% |
| Rottweil R 903 | <<locked>> | 80% | 51,822 psi | 81% | 3245 fps | 100% |
| Rottweil R 904 | <<locked>> | 84% | 44,396 psi | 70% | 3120 fps | 95.6% |
| Rottweil R 905 | <<locked>> | 82% | 39,334 psi | 62% | 3048 fps | 95.4% |
| Rottweil R 907 | <<locked>> | 80% | 47,558 psi | 75% | 3169 fps | 98.4% |
| Shooters World Long Rifle | <<locked>> | 80% | 46,383 psi | 73% | 3143 fps | 99.4% |
| Shooters World SW4350 | <<locked>> | 80% | 44,889 psi | 70% | 3127 fps | 98.5% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 53,345 psi | 84% | 3307 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 52,011 psi | 82% | 3117 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 45,542 psi | 71% | 3081 fps | 98.5% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 39,001 psi | 61% | 3045 fps | 95.2% |
| Somchem S355 | <<locked>> | 80% | 51,503 psi | 81% | 3238 fps | 100% |
| Somchem S361 | <<locked>> | 84% | 45,382 psi | 71% | 3104 fps | 95.1% |
| Somchem S365 | <<locked>> | 80% | 40,973 psi | 64% | 3094 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 37,173 psi | 58% | 2963 fps | 95.6% |
| Vihtavuori N150 | <<locked>> | 80% | 49,545 psi | 78% | 3156 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 45,513 psi | 71% | 3146 fps | 99.8% |
| Vihtavuori N165 | <<locked>> | 84% | 36,869 psi | 58% | 2943 fps | 95.1% |
| Vihtavuori N550 | <<locked>> | 80% | 44,846 psi | 70% | 3143 fps | 99.7% |
| Vihtavuori N555 | <<locked>> | 80% | 35,694 psi | 56% | 2972 fps | 98.7% |
| Vihtavuori N560 | 65.3 gr | 88% | 46,862 psi | 73% | 3278 fps | 95.7% |
| Vihtavuori N565 | <<locked>> | 92% | 43,613 psi | 68% | 3179 fps | 95.1% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 44,817 psi | 70% | 3100 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 46,702 psi | 73% | 3219 fps | 98.7% |
| Winchester StaBALL HD | 58.7 gr | 80% | 28,137 psi | 44% | 2871 fps | 98.5% |
| Winchester Supreme 780 | <<locked>> | 84% | 39,262 psi | 62% | 3009 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 75 powders for .257 Weath. Mag. loaded with the .257 | 100gr | Osprey Virtus. Winchester StaBALL HD delivers the highest muzzle velocity at 3,537 fps; across all powders the maximum-charge window runs from 2,175 fps to 3,537 fps. ADI AR 2217 gives the best case fill at 100 %, and 75 of the 75 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 1:10.0 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 | Osprey Virtus 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.