Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 88gr | Osprey Virtus bullet and 84 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Accurate High Country, Norma MRP and Alliant Reloder-16.
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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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 2700 | <<locked>> | 82% | 57,217 psi | 90% | 3478 fps | 98.9% |
| Accurate 3100 | <<locked>> | 98% | 57,363 psi | 90% | 3527 fps | 99.8% |
| Accurate 4064 | <<locked>> | 82% | 56,304 psi | 88% | 3458 fps | 100% |
| Accurate 4350 | <<locked>> | 88% | 54,665 psi | 86% | 3524 fps | 100% |
| Accurate High Country | <<locked>> | 94% | 55,143 psi | 86% | 3629 fps | 97.3% |
| Accurate MAGPRO | <<locked>> | 96% | 56,202 psi | 88% | 3625 fps | 96.2% |
| ADI AR 2208 | <<locked>> | 84% | 56,594 psi | 89% | 3507 fps | 100% |
| ADI AR 2209 | <<locked>> | 94% | 56,202 psi | 88% | 3579 fps | 98.2% |
| ADI AR 2213 | <<locked>> | 96% | 53,853 psi | 84% | 3563 fps | 96.7% |
| Alliant Power Pro Varmint | <<locked>> | 94% | 56,231 psi | 88% | 3570 fps | 98.3% |
| Alliant Power Pro Varmint | <<locked>> | 94% | 56,231 psi | 88% | 3570 fps | 98.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 57,450 psi | 90% | 3527 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 82% | 57,653 psi | 90% | 3556 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 90% | 55,840 psi | 88% | 3599 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 86% | 57,246 psi | 90% | 3619 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 94% | 55,477 psi | 87% | 3556 fps | 98.2% |
| Alliant Reloder-22 | <<locked>> | 98% | 57,479 psi | 90% | 3635 fps | 98.6% |
| Alliant Reloder-23 | <<locked>> | 98% | 54,447 psi | 85% | 3547 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 50,444 psi | 79% | 3530 fps | 99.8% |
| Alliant Reloder-26 | <<locked>> | 94% | 54,984 psi | 86% | 3638 fps | 100% |
| Bofors RP15ᴾ | <<locked>> | 100% | 56,318 psi | 88% | 3609 fps | 98.4% |
| Bofors RP3 | <<locked>> | 82% | 54,723 psi | 86% | 3481 fps | 100% |
| Bofors RP5 | <<locked>> | 98% | 57,479 psi | 90% | 3635 fps | 98.6% |
| Bofors RP7 | <<locked>> | 88% | 57,696 psi | 90% | 3530 fps | 99.1% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 49,806 psi | 78% | 3461 fps | 96.7% |
| Hodgdon H380 | <<locked>> | 82% | 55,158 psi | 86% | 3501 fps | 99.9% |
| Hodgdon H414 | <<locked>> | 88% | 57,014 psi | 89% | 3586 fps | 99.4% |
| Hodgdon H4350 | <<locked>> | 86% | 55,941 psi | 88% | 3537 fps | 98.4% |
| Hodgdon H4831 | <<locked>> | 94% | 53,896 psi | 84% | 3497 fps | 96% |
| Hodgdon H4831 SC | <<locked>> | 96% | 56,565 psi | 89% | 3550 fps | 96.6% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 55,985 psi | 88% | 3501 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 49,400 psi | 77% | 3579 fps | 98% |
| Hodgdon Superformance | <<locked>> | 86% | 53,751 psi | 84% | 3550 fps | 98.9% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,492 psi | 57% | 2300 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 55,825 psi | 87% | 3484 fps | 100% |
| IMR 4350 | <<locked>> | 90% | 55,811 psi | 87% | 3504 fps | 98.9% |
| IMR 4451 Enduron | <<locked>> | 86% | 55,796 psi | 87% | 3497 fps | 99.1% |
| IMR 4831 | <<locked>> | 90% | 55,187 psi | 86% | 3510 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 94% | 55,274 psi | 87% | 3491 fps | 96.5% |
| IMR 7828 SSC | <<locked>> | 98% | 55,259 psi | 87% | 3606 fps | 97.1% |
| Lovex S062 | <<locked>> | 82% | 56,028 psi | 88% | 3474 fps | 100% |
| Lovex S065 | <<locked>> | 88% | 56,072 psi | 88% | 3491 fps | 99.8% |
| Lovex S070 | <<locked>> | 88% | 54,157 psi | 85% | 3478 fps | 99.1% |
| Lovex S071ᴾ | <<locked>> | 100% | 50,647 psi | 79% | 3409 fps | 99.2% |
| Norma 203B | <<locked>> | 82% | 56,956 psi | 89% | 3537 fps | 100% |
| Norma 204 | <<locked>> | 90% | 57,101 psi | 89% | 3570 fps | 98.2% |
| Norma MRP | <<locked>> | 96% | 57,450 psi | 90% | 3661 fps | 99.5% |
| Norma URP | <<locked>> | 90% | 57,261 psi | 90% | 3573 fps | 100% |
| Ramshot Grand | <<locked>> | 98% | 56,202 psi | 88% | 3629 fps | 97.7% |
| Ramshot Hunter | <<locked>> | 90% | 56,289 psi | 88% | 3570 fps | 99.7% |
| Ramshot Magnumᴾ | <<locked>> | 100% | 54,737 psi | 86% | 3550 fps | 98.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,246 psi | 58% | 2356 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 55,071 psi | 86% | 3484 fps | 99.4% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 56,637 psi | 89% | 3609 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 54,868 psi | 86% | 3540 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 57,682 psi | 90% | 3648 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 50,024 psi | 78% | 3573 fps | 99.1% |
| Rottweil R 903 | <<locked>> | 84% | 55,085 psi | 86% | 3481 fps | 100% |
| Rottweil R 904 | <<locked>> | 94% | 57,551 psi | 90% | 3543 fps | 97.5% |
| Rottweil R 905 | <<locked>> | 94% | 54,795 psi | 86% | 3543 fps | 98.2% |
| Rottweil R 907 | <<locked>> | 88% | 57,696 psi | 90% | 3530 fps | 99.1% |
| Shooters World Long Rifle | <<locked>> | 88% | 56,072 psi | 88% | 3491 fps | 99.8% |
| Shooters World Precision | <<locked>> | 82% | 56,028 psi | 88% | 3474 fps | 100% |
| Shooters World SW4350 | <<locked>> | 88% | 54,157 psi | 85% | 3478 fps | 99.1% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 56,971 psi | 89% | 3547 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 55,347 psi | 87% | 3346 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 88% | 55,898 psi | 88% | 3438 fps | 99.3% |
| SNPE Vectan Tubal 8000 | <<locked>> | 94% | 54,331 psi | 85% | 3537 fps | 98.1% |
| Somchem S355 | <<locked>> | 84% | 54,810 psi | 86% | 3474 fps | 100% |
| Somchem S361 | <<locked>> | 92% | 55,680 psi | 87% | 3458 fps | 96.4% |
| Somchem S365 | <<locked>> | 92% | 57,188 psi | 90% | 3570 fps | 100% |
| Somchem S385 | <<locked>> | 94% | 55,550 psi | 87% | 3514 fps | 98.9% |
| Vihtavuori N150 | <<locked>> | 86% | 56,347 psi | 88% | 3445 fps | 100% |
| Vihtavuori N160 | <<locked>> | 88% | 55,332 psi | 87% | 3497 fps | 100% |
| Vihtavuori N165 | <<locked>> | 98% | 55,056 psi | 86% | 3481 fps | 98.6% |
| Vihtavuori N540 | <<locked>> | 82% | 57,058 psi | 89% | 3445 fps | 100% |
| Vihtavuori N550 | <<locked>> | 88% | 54,621 psi | 86% | 3501 fps | 100% |
| Vihtavuori N555 | <<locked>> | 96% | 56,478 psi | 89% | 3576 fps | 100% |
| Vihtavuori N560 | <<locked>> | 96% | 57,348 psi | 90% | 3648 fps | 97.1% |
| Vihtavuori N565ᴾ | <<locked>> | 100% | 52,895 psi | 83% | 3530 fps | 96.4% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 55,303 psi | 87% | 3451 fps | 100% |
| Winchester 760 | <<locked>> | 88% | 57,014 psi | 89% | 3586 fps | 99.4% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 55,666 psi | 87% | 3694 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 96% | 55,927 psi | 88% | 3507 fps | 98.2% |
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% | 53,461 psi | 84% | 3409 fps | 98.4% |
| Accurate 3100 | <<locked>> | 84% | 34,679 psi | 54% | 3035 fps | 95% |
| Accurate 4064 | <<locked>> | 80% | 52,750 psi | 83% | 3399 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 41,075 psi | 64% | 3238 fps | 98.6% |
| Accurate High Country | 67.7 gr | 90% | 47,601 psi | 75% | 3468 fps | 95.3% |
| Accurate MAGPRO | <<locked>> | 94% | 52,272 psi | 82% | 3543 fps | 95.2% |
| ADI AR 2208 | <<locked>> | 80% | 49,763 psi | 78% | 3379 fps | 99.9% |
| ADI AR 2209 | <<locked>> | 88% | 45,643 psi | 72% | 3360 fps | 95.8% |
| ADI AR 2213 | <<locked>> | 94% | 50,328 psi | 79% | 3488 fps | 95.8% |
| Alliant Power Pro Varmint | <<locked>> | 88% | 45,861 psi | 72% | 3360 fps | 95.9% |
| Alliant Power Pro Varmint | <<locked>> | 88% | 45,861 psi | 72% | 3360 fps | 95.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 50,502 psi | 79% | 3406 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 54,056 psi | 85% | 3494 fps | 100% |
| Alliant Reloder-16 | 56.1 gr | 80% | 39,508 psi | 62% | 3251 fps | 98.6% |
| Alliant Reloder-17 | <<locked>> | 80% | 45,876 psi | 72% | 3406 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 88% | 45,353 psi | 71% | 3346 fps | 95.8% |
| Alliant Reloder-22 | <<locked>> | 90% | 43,381 psi | 68% | 3340 fps | 95.3% |
| Alliant Reloder-23 | <<locked>> | 80% | 29,022 psi | 45% | 2936 fps | 96.3% |
| Alliant Reloder-25 | <<locked>> | 88% | 33,402 psi | 52% | 3087 fps | 95% |
| Alliant Reloder-26 | <<locked>> | 82% | 34,113 psi | 53% | 3153 fps | 96.2% |
| Bofors RP15 | <<locked>> | 94% | 45,788 psi | 72% | 3392 fps | 95.9% |
| Bofors RP3 | <<locked>> | 80% | 51,184 psi | 80% | 3415 fps | 100% |
| Bofors RP5 | <<locked>> | 90% | 43,381 psi | 68% | 3340 fps | 95.3% |
| Bofors RP7 | <<locked>> | 80% | 44,527 psi | 70% | 3264 fps | 96.6% |
| Hodgdon H1000 | <<locked>> | 98% | 46,224 psi | 72% | 3379 fps | 95.6% |
| Hodgdon H380 | <<locked>> | 80% | 51,445 psi | 81% | 3432 fps | 99.7% |
| Hodgdon H414 | <<locked>> | 80% | 43,178 psi | 68% | 3301 fps | 96.8% |
| Hodgdon H4350 | <<locked>> | 80% | 45,876 psi | 72% | 3327 fps | 96.2% |
| Hodgdon H4831 | <<locked>> | 92% | 50,372 psi | 79% | 3425 fps | 95.1% |
| Hodgdon H4831 SC | <<locked>> | 94% | 52,881 psi | 83% | 3478 fps | 95.8% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 37,159 psi | 58% | 3120 fps | 99% |
| Hodgdon Retumbo | <<locked>> | 96% | 42,989 psi | 67% | 3415 fps | 95.9% |
| Hodgdon Superformance | <<locked>> | 80% | 42,496 psi | 67% | 3304 fps | 96.3% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,137 psi | 43% | 2064 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 52,344 psi | 82% | 3422 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 40,074 psi | 63% | 3166 fps | 95.3% |
| IMR 4451 Enduron | <<locked>> | 80% | 46,108 psi | 72% | 3301 fps | 97.5% |
| IMR 4831 | <<locked>> | 80% | 39,291 psi | 62% | 3179 fps | 98.3% |
| IMR 4955 Enduron | <<locked>> | 92% | 51,634 psi | 81% | 3419 fps | 95.7% |
| IMR 7828 SSC | <<locked>> | 94% | 47,950 psi | 75% | 3448 fps | 95.2% |
| Lovex S062 | <<locked>> | 80% | 52,518 psi | 82% | 3412 fps | 100% |
| Lovex S065 | <<locked>> | 80% | 43,395 psi | 68% | 3235 fps | 98.1% |
| Lovex S070 | <<locked>> | 80% | 41,611 psi | 65% | 3209 fps | 96.6% |
| Lovex S071 | <<locked>> | 90% | 36,071 psi | 57% | 3074 fps | 95.6% |
| Norma 203B | <<locked>> | 80% | 53,403 psi | 84% | 3474 fps | 100% |
| Norma 204 | <<locked>> | 84% | 46,079 psi | 72% | 3346 fps | 95.8% |
| Norma MRP | 64.7 gr | 86% | 39,595 psi | 62% | 3274 fps | 95.6% |
| Norma URP | <<locked>> | 80% | 40,553 psi | 64% | 3228 fps | 98.4% |
| Ramshot Grand | <<locked>> | 94% | 48,196 psi | 76% | 3461 fps | 95.7% |
| Ramshot Hunter | <<locked>> | 80% | 39,552 psi | 62% | 3209 fps | 96.6% |
| Ramshot Magnum | <<locked>> | 92% | 39,943 psi | 63% | 3228 fps | 95.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,673 psi | 43% | 2113 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 51,445 psi | 81% | 3412 fps | 99% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 48,776 psi | 76% | 3471 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 41,089 psi | 64% | 3258 fps | 98.4% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 39,697 psi | 62% | 3268 fps | 97.9% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 39,871 psi | 62% | 3310 fps | 96% |
| Rottweil R 903 | <<locked>> | 80% | 47,964 psi | 75% | 3350 fps | 100% |
| Rottweil R 904 | <<locked>> | 88% | 47,021 psi | 74% | 3333 fps | 95% |
| Rottweil R 905 | <<locked>> | 88% | 44,454 psi | 70% | 3327 fps | 95.7% |
| Rottweil R 907 | <<locked>> | 80% | 44,527 psi | 70% | 3264 fps | 96.6% |
| Shooters World Long Rifle | <<locked>> | 80% | 43,395 psi | 68% | 3235 fps | 98.1% |
| Shooters World Precision | <<locked>> | 80% | 52,518 psi | 82% | 3412 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 41,611 psi | 65% | 3209 fps | 96.6% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 49,588 psi | 78% | 3412 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 48,762 psi | 76% | 3238 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 42,554 psi | 67% | 3169 fps | 96.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 44,063 psi | 69% | 3317 fps | 95.5% |
| Somchem S355 | <<locked>> | 80% | 48,124 psi | 75% | 3350 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 52,040 psi | 82% | 3389 fps | 95.6% |
| Somchem S365 | <<locked>> | 80% | 37,144 psi | 58% | 3173 fps | 99.8% |
| Somchem S385 | <<locked>> | 86% | 42,047 psi | 66% | 3232 fps | 95.9% |
| Vihtavuori N150 | <<locked>> | 80% | 46,021 psi | 72% | 3261 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 42,177 psi | 66% | 3235 fps | 98.7% |
| Vihtavuori N165 | <<locked>> | 90% | 41,872 psi | 66% | 3212 fps | 95.5% |
| Vihtavuori N540 | <<locked>> | 80% | 53,359 psi | 84% | 3386 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 41,539 psi | 65% | 3228 fps | 98.4% |
| Vihtavuori N555 | <<locked>> | 80% | 32,300 psi | 51% | 3025 fps | 96.3% |
| Vihtavuori N560 | <<locked>> | 92% | 49,632 psi | 78% | 3494 fps | 95.2% |
| Vihtavuori N565 | <<locked>> | 98% | 49,139 psi | 77% | 3455 fps | 95.4% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 41,379 psi | 65% | 3189 fps | 99.9% |
| Winchester 760 | <<locked>> | 80% | 43,178 psi | 68% | 3301 fps | 96.8% |
| Winchester StaBALL HD | <<locked>> | 82% | 27,543 psi | 43% | 2972 fps | 96.4% |
| Winchester Supreme 780 | <<locked>> | 90% | 44,773 psi | 70% | 3284 fps | 95.7% |
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 84 powders for .257 Weath. Mag. loaded with the .257 | 88gr | Osprey Virtus. Winchester StaBALL HD delivers the highest muzzle velocity at 3,694 fps; across all powders the maximum-charge window runs from 2,300 fps to 3,694 fps. Alliant Reloder-25 gives the best case fill at 100 %, and 84 of the 84 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 57–90 %, leaving at least 10 % headroom. The 88.0 gr projectile in 0.257" calls for a 1:10.5 twist; slower twists will usually not stabilise this weight. Alliant Reloder-25, Bofors RP15, Hodgdon H1000 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. Accurate High Country, Norma MRP, Alliant Reloder-16 rank at the top here: for .257 Weath. Mag. with the .257 | 88gr | 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.