Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 70gr | Impala LWHV LS bullet and 79 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-26, Alliant Reloder-16 and ReloadSwiss RS 70.
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>> | 86% | 56,086 psi | 88% | 3701 fps | 97% |
| Accurate 3100 | <<locked>> | 98% | 54,302 psi | 85% | 3740 fps | 98.3% |
| Accurate 4064 | <<locked>> | 82% | 54,940 psi | 86% | 3737 fps | 100% |
| Accurate 4350 | <<locked>> | 90% | 55,550 psi | 87% | 3825 fps | 99.5% |
| ADI AR 2208 | <<locked>> | 86% | 56,985 psi | 89% | 3809 fps | 99.8% |
| ADI AR 2209 | <<locked>> | 96% | 55,956 psi | 88% | 3845 fps | 96.1% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 56,420 psi | 88% | 3950 fps | 99.8% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 54,781 psi | 86% | 3780 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 82% | 54,781 psi | 86% | 3802 fps | 99.7% |
| Alliant Reloder-16 | <<locked>> | 92% | 55,129 psi | 86% | 3885 fps | 99.7% |
| Alliant Reloder-17 | <<locked>> | 88% | 56,855 psi | 89% | 3921 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 96% | 55,506 psi | 87% | 3829 fps | 96.2% |
| Alliant Reloder-22ᴾ | <<locked>> | 100% | 57,043 psi | 89% | 3898 fps | 96.7% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 53,766 psi | 84% | 3829 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 47,195 psi | 74% | 3714 fps | 97.8% |
| Alliant Reloder-26 | <<locked>> | 96% | 54,346 psi | 85% | 3917 fps | 99.5% |
| Bofors RP3 | <<locked>> | 84% | 56,072 psi | 88% | 3802 fps | 100% |
| Bofors RP5ᴾ | <<locked>> | 100% | 57,043 psi | 89% | 3898 fps | 96.7% |
| Bofors RP7 | <<locked>> | 88% | 55,158 psi | 86% | 3757 fps | 97% |
| Hodgdon H380 | <<locked>> | 84% | 56,231 psi | 88% | 3809 fps | 99.2% |
| Hodgdon H414 | <<locked>> | 86% | 54,563 psi | 86% | 3822 fps | 97.5% |
| Hodgdon H4350 | <<locked>> | 90% | 54,708 psi | 86% | 3786 fps | 96.2% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 55,927 psi | 88% | 3796 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 84% | 57,334 psi | 90% | 3862 fps | 100% |
| Hodgdon Superformance | <<locked>> | 88% | 53,693 psi | 84% | 3822 fps | 97.1% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,564 psi | 57% | 2543 fps | 100% |
| Hodgdon VARGET | <<locked>> | 84% | 56,449 psi | 88% | 3806 fps | 100% |
| IMR 3031 | <<locked>> | 82% | 55,680 psi | 87% | 3793 fps | 100% |
| IMR 4064 | <<locked>> | 86% | 55,724 psi | 87% | 3776 fps | 99.8% |
| IMR 4166 Enduron | <<locked>> | 86% | 54,737 psi | 86% | 3734 fps | 97.4% |
| IMR 4350 | <<locked>> | 92% | 56,028 psi | 88% | 3780 fps | 97.3% |
| IMR 4451 Enduron | <<locked>> | 88% | 56,362 psi | 88% | 3786 fps | 97.7% |
| IMR 4831 | <<locked>> | 96% | 56,608 psi | 89% | 3822 fps | 99.6% |
| IMR 4895 | <<locked>> | 82% | 56,202 psi | 88% | 3842 fps | 99.9% |
| Lovex S060 | <<locked>> | 82% | 57,653 psi | 90% | 3776 fps | 100% |
| Lovex S062 | <<locked>> | 84% | 57,058 psi | 89% | 3789 fps | 100% |
| Lovex S065 | <<locked>> | 90% | 57,087 psi | 89% | 3789 fps | 98.9% |
| Lovex S070 | <<locked>> | 90% | 55,129 psi | 86% | 3770 fps | 97.7% |
| Lovex S071ᴾ | <<locked>> | 100% | 48,414 psi | 76% | 3622 fps | 97.1% |
| Norma 203B | <<locked>> | 82% | 54,186 psi | 85% | 3783 fps | 99.8% |
| Norma 204 | <<locked>> | 92% | 56,985 psi | 89% | 3835 fps | 96.2% |
| Norma MRP | <<locked>> | 98% | 56,724 psi | 89% | 3930 fps | 98% |
| Norma URP | <<locked>> | 92% | 57,159 psi | 90% | 3862 fps | 99.6% |
| Ramshot Big Game | <<locked>> | 82% | 54,926 psi | 86% | 3802 fps | 99.8% |
| Ramshot Hunter | <<locked>> | 92% | 56,072 psi | 88% | 3845 fps | 98.5% |
| Ramshot Magnumᴾ | <<locked>> | 100% | 56,811 psi | 89% | 3842 fps | 97.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,130 psi | 58% | 2598 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 84% | 55,840 psi | 88% | 3773 fps | 98.2% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 56,202 psi | 88% | 3921 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 90% | 55,201 psi | 87% | 3835 fps | 99.3% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 57,246 psi | 90% | 3930 fps | 99.5% |
| Rottweil R 902 | <<locked>> | 82% | 55,767 psi | 87% | 3753 fps | 100% |
| Rottweil R 903 | <<locked>> | 86% | 56,101 psi | 88% | 3793 fps | 100% |
| Rottweil R 905 | <<locked>> | 96% | 54,694 psi | 86% | 3809 fps | 96.1% |
| Rottweil R 907 | <<locked>> | 88% | 55,158 psi | 86% | 3757 fps | 97% |
| Shooters World Long Rifle | <<locked>> | 90% | 57,087 psi | 89% | 3789 fps | 98.9% |
| Shooters World Precision | <<locked>> | 84% | 57,058 psi | 89% | 3789 fps | 100% |
| Shooters World SW4350 | <<locked>> | 90% | 55,129 psi | 86% | 3770 fps | 97.7% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 57,188 psi | 90% | 3852 fps | 99.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 56,173 psi | 88% | 3661 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 90% | 56,985 psi | 89% | 3724 fps | 97.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 96% | 54,215 psi | 85% | 3802 fps | 95.9% |
| Somchem S355 | <<locked>> | 86% | 55,985 psi | 88% | 3789 fps | 100% |
| Somchem S365 | <<locked>> | 94% | 56,782 psi | 89% | 3871 fps | 100% |
| Somchem S385 | <<locked>> | 96% | 55,811 psi | 87% | 3786 fps | 97.2% |
| Unknown powder | <<locked>> | 90% | 57,537 psi | 90% | 3868 fps | 99.3% |
| Vihtavuori N133 | <<locked>> | 82% | 55,114 psi | 86% | 3652 fps | 100% |
| Vihtavuori N135 | <<locked>> | 82% | 55,753 psi | 87% | 3711 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 55,027 psi | 86% | 3704 fps | 100% |
| Vihtavuori N150 | <<locked>> | 92% | 57,522 psi | 90% | 3766 fps | 100% |
| Vihtavuori N160 | <<locked>> | 88% | 54,578 psi | 86% | 3763 fps | 99.3% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 53,156 psi | 83% | 3707 fps | 96.3% |
| Vihtavuori N540 | <<locked>> | 82% | 55,230 psi | 87% | 3734 fps | 100% |
| Vihtavuori N550 | <<locked>> | 88% | 55,129 psi | 86% | 3822 fps | 99.3% |
| Vihtavuori N555 | <<locked>> | 98% | 56,550 psi | 89% | 3871 fps | 99.8% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 55,579 psi | 87% | 3740 fps | 100% |
| Winchester 760 | <<locked>> | 86% | 54,563 psi | 86% | 3822 fps | 97.5% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 49,327 psi | 77% | 3894 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 96% | 57,624 psi | 90% | 3802 fps | 96.6% |
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>> | 82% | 49,356 psi | 77% | 3563 fps | 95.4% |
| Accurate 3100 | <<locked>> | 90% | 41,640 psi | 65% | 3461 fps | 95.1% |
| Accurate 4064 | <<locked>> | 80% | 51,677 psi | 81% | 3681 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 39,813 psi | 62% | 3468 fps | 96.2% |
| ADI AR 2208 | <<locked>> | 80% | 47,311 psi | 74% | 3606 fps | 98.7% |
| ADI AR 2209 | <<locked>> | 94% | 52,257 psi | 82% | 3766 fps | 95.2% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 52,431 psi | 82% | 3865 fps | 99.5% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 48,283 psi | 76% | 3645 fps | 99.7% |
| Alliant Reloder-15 | <<locked>> | 80% | 51,561 psi | 81% | 3734 fps | 99.3% |
| Alliant Reloder-16 | 56.5 gr | 80% | 37,724 psi | 59% | 3455 fps | 95.8% |
| Alliant Reloder-17 | <<locked>> | 80% | 43,076 psi | 68% | 3622 fps | 99% |
| Alliant Reloder-19 | <<locked>> | 94% | 51,938 psi | 81% | 3753 fps | 95.2% |
| Alliant Reloder-22 | <<locked>> | 98% | 53,243 psi | 83% | 3822 fps | 95.8% |
| Alliant Reloder-23 | <<locked>> | 84% | 32,358 psi | 51% | 3281 fps | 95.3% |
| Alliant Reloder-25 | <<locked>> | 96% | 41,582 psi | 65% | 3563 fps | 95.9% |
| Alliant Reloder-26 | 67.1 gr | 86% | 37,927 psi | 59% | 3507 fps | 95.2% |
| Bofors RP3 | <<locked>> | 80% | 49,313 psi | 77% | 3668 fps | 99.8% |
| Bofors RP5 | <<locked>> | 98% | 53,243 psi | 83% | 3822 fps | 95.8% |
| Bofors RP7 | <<locked>> | 84% | 48,704 psi | 76% | 3615 fps | 95.4% |
| Hodgdon H380 | <<locked>> | 80% | 49,255 psi | 77% | 3665 fps | 98.2% |
| Hodgdon H414 | <<locked>> | 82% | 47,543 psi | 75% | 3665 fps | 95.8% |
| Hodgdon H4350 | <<locked>> | 88% | 51,503 psi | 81% | 3717 fps | 95.4% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 35,592 psi | 56% | 3333 fps | 96.8% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 50,241 psi | 79% | 3727 fps | 99.9% |
| Hodgdon Superformance | <<locked>> | 84% | 46,514 psi | 73% | 3658 fps | 95.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,398 psi | 43% | 2290 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 49,937 psi | 78% | 3675 fps | 99.6% |
| IMR 3031 | <<locked>> | 80% | 52,417 psi | 82% | 3734 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 46,514 psi | 73% | 3583 fps | 98.7% |
| IMR 4166 Enduron | <<locked>> | 80% | 45,745 psi | 72% | 3533 fps | 95.2% |
| IMR 4350 | <<locked>> | 88% | 49,501 psi | 78% | 3642 fps | 95.7% |
| IMR 4451 Enduron | <<locked>> | 82% | 46,891 psi | 73% | 3579 fps | 95.4% |
| IMR 4831 | <<locked>> | 82% | 36,753 psi | 58% | 3363 fps | 95.3% |
| IMR 4895 | <<locked>> | 80% | 52,823 psi | 83% | 3773 fps | 99.7% |
| Lovex S060 | <<locked>> | 80% | 54,273 psi | 85% | 3714 fps | 99.8% |
| Lovex S062 | <<locked>> | 80% | 50,546 psi | 79% | 3665 fps | 99.9% |
| Lovex S065 | <<locked>> | 80% | 42,177 psi | 66% | 3461 fps | 95.6% |
| Lovex S070 | <<locked>> | 84% | 45,861 psi | 72% | 3563 fps | 95.5% |
| Lovex S071 | <<locked>> | 96% | 42,786 psi | 67% | 3491 fps | 95.5% |
| Norma 203B | <<locked>> | 80% | 50,952 psi | 80% | 3717 fps | 99.5% |
| Norma 204 | <<locked>> | 90% | 53,301 psi | 84% | 3763 fps | 95.3% |
| Norma MRP | <<locked>> | 92% | 46,209 psi | 72% | 3698 fps | 95.3% |
| Norma URP | <<locked>> | 80% | 38,856 psi | 61% | 3445 fps | 95.8% |
| Ramshot Big Game | <<locked>> | 80% | 51,213 psi | 80% | 3727 fps | 99.5% |
| Ramshot Hunter | <<locked>> | 84% | 43,076 psi | 68% | 3556 fps | 95.4% |
| Ramshot Magnum | <<locked>> | 96% | 48,921 psi | 77% | 3678 fps | 95.4% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,760 psi | 44% | 2339 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 49,153 psi | 77% | 3632 fps | 96.8% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 45,556 psi | 71% | 3707 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 39,175 psi | 61% | 3465 fps | 95.7% |
| ReloadSwiss RS 70 | 63.4 gr | 82% | 40,640 psi | 64% | 3540 fps | 95.8% |
| Rottweil R 902 | <<locked>> | 80% | 52,446 psi | 82% | 3691 fps | 100% |
| Rottweil R 903 | <<locked>> | 80% | 46,383 psi | 73% | 3596 fps | 99.4% |
| Rottweil R 905 | <<locked>> | 94% | 51,300 psi | 80% | 3740 fps | 95.2% |
| Rottweil R 907 | <<locked>> | 84% | 48,704 psi | 76% | 3615 fps | 95.4% |
| Shooters World Long Rifle | <<locked>> | 80% | 42,177 psi | 66% | 3461 fps | 95.6% |
| Shooters World Precision | <<locked>> | 80% | 50,546 psi | 79% | 3665 fps | 99.9% |
| Shooters World SW4350 | <<locked>> | 84% | 45,861 psi | 72% | 3563 fps | 95.5% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 46,949 psi | 74% | 3638 fps | 99% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 46,775 psi | 73% | 3491 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 47,050 psi | 74% | 3517 fps | 95.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 94% | 50,836 psi | 80% | 3730 fps | 95.1% |
| Somchem S355 | <<locked>> | 80% | 46,412 psi | 73% | 3593 fps | 99.3% |
| Somchem S365 | <<locked>> | 80% | 35,447 psi | 56% | 3392 fps | 98.2% |
| Somchem S385 | <<locked>> | 92% | 49,139 psi | 77% | 3648 fps | 95.6% |
| Unknown powder | <<locked>> | 80% | 41,698 psi | 65% | 3517 fps | 96% |
| Vihtavuori N133 | <<locked>> | 80% | 51,822 psi | 81% | 3596 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 52,330 psi | 82% | 3652 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 51,706 psi | 81% | 3645 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 40,001 psi | 63% | 3399 fps | 99.1% |
| Vihtavuori N160 | <<locked>> | 80% | 41,916 psi | 66% | 3484 fps | 96.8% |
| Vihtavuori N165 | <<locked>> | 98% | 49,719 psi | 78% | 3635 fps | 95.4% |
| Vihtavuori N540 | <<locked>> | 80% | 51,808 psi | 81% | 3671 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 42,583 psi | 67% | 3540 fps | 96.8% |
| Vihtavuori N555 | <<locked>> | 84% | 36,056 psi | 56% | 3392 fps | 95.6% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 39,639 psi | 62% | 3399 fps | 98.5% |
| Winchester 760 | <<locked>> | 82% | 47,543 psi | 75% | 3665 fps | 95.8% |
| Winchester StaBALL HD | <<locked>> | 86% | 31,096 psi | 49% | 3317 fps | 95.4% |
| Winchester Supreme 780 | <<locked>> | 94% | 53,751 psi | 84% | 3727 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 79 powders for .257 Weath. Mag. loaded with the .257 | 70gr | Impala LWHV LS. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,950 fps; across all powders the maximum-charge window runs from 2,543 fps to 3,950 fps. Alliant Reloder-22 gives the best case fill at 100 %, and 79 of the 79 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 70.0 gr projectile in 0.257" calls for a 1:10.0 twist; slower twists will usually not stabilise this weight. Alliant Reloder-22, Alliant Reloder-23, 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-26, Alliant Reloder-16, ReloadSwiss RS 70 rank at the top here: for .257 Weath. Mag. with the .257 | 70gr | Impala LWHV LS 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.