Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 115gr | Nosler Partition bullet and 71 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-25, Hodgdon Retumbo and ReloadSwiss RS 76.
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>> | 92% | 57,609 psi | 90% | 3176 fps | 100% |
| Accurate 4350 | <<locked>> | 82% | 54,418 psi | 85% | 3143 fps | 100% |
| Accurate High Country | <<locked>> | 88% | 55,506 psi | 87% | 3281 fps | 99.3% |
| Accurate MAGPRO | <<locked>> | 90% | 56,463 psi | 88% | 3284 fps | 98.6% |
| ADI AR 2209 | <<locked>> | 88% | 55,317 psi | 87% | 3209 fps | 99.7% |
| ADI AR 2213 | <<locked>> | 92% | 57,305 psi | 90% | 3284 fps | 99.4% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 55,521 psi | 87% | 3245 fps | 99.5% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 49,893 psi | 78% | 3199 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 84% | 55,521 psi | 87% | 3205 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 88% | 55,100 psi | 86% | 3199 fps | 99.7% |
| Alliant Reloder-22 | <<locked>> | 92% | 57,537 psi | 90% | 3278 fps | 99.9% |
| Alliant Reloder-23 | <<locked>> | 92% | 55,390 psi | 87% | 3182 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 96% | 54,955 psi | 86% | 3251 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 88% | 55,811 psi | 87% | 3274 fps | 100% |
| Alliant Reloder-33ᴾ | <<locked>> | 100% | 52,605 psi | 82% | 3258 fps | 96.3% |
| Baschieri & Pellagri 109 | <<locked>> | 92% | 54,708 psi | 86% | 3169 fps | 96.8% |
| Bofors RP15 | <<locked>> | 94% | 56,695 psi | 89% | 3261 fps | 99.8% |
| Bofors RP30 | <<locked>> | 98% | 54,810 psi | 86% | 3255 fps | 99.4% |
| Bofors RP5 | <<locked>> | 92% | 57,537 psi | 90% | 3278 fps | 99.9% |
| Bofors RP7 | <<locked>> | 82% | 56,188 psi | 88% | 3146 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 98% | 57,072 psi | 89% | 3271 fps | 99.8% |
| Hodgdon H414 | <<locked>> | 82% | 56,101 psi | 88% | 3205 fps | 100% |
| Hodgdon H4831 | <<locked>> | 90% | 56,855 psi | 89% | 3212 fps | 98.9% |
| Hodgdon H4831 SC | <<locked>> | 90% | 55,782 psi | 87% | 3196 fps | 98.7% |
| Hodgdon Hybrid 100V | <<locked>> | 86% | 55,825 psi | 87% | 3123 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 53,969 psi | 85% | 3333 fps | 100% |
| Hodgdon Superformance | <<locked>> | 82% | 56,666 psi | 89% | 3238 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,420 psi | 59% | 2041 fps | 100% |
| IMR 4350 | <<locked>> | 84% | 54,505 psi | 85% | 3130 fps | 99.9% |
| IMR 4451 Enduron | <<locked>> | 82% | 57,609 psi | 90% | 3169 fps | 100% |
| IMR 4831 | <<locked>> | 84% | 54,998 psi | 86% | 3136 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 90% | 57,348 psi | 90% | 3189 fps | 99% |
| IMR 7828 SSC | <<locked>> | 92% | 55,419 psi | 87% | 3261 fps | 99.2% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 45,426 psi | 71% | 3097 fps | 97.9% |
| Lovex S065 | <<locked>> | 82% | 54,955 psi | 86% | 3110 fps | 100% |
| Lovex S070 | <<locked>> | 84% | 56,739 psi | 89% | 3163 fps | 100% |
| Lovex S071 | <<locked>> | 96% | 55,187 psi | 86% | 3136 fps | 100% |
| Norma 204 | <<locked>> | 84% | 55,709 psi | 87% | 3192 fps | 99.6% |
| Norma 217ᴾ | <<locked>> | 100% | 46,006 psi | 72% | 3130 fps | 99.5% |
| Norma MRP | <<locked>> | 90% | 57,493 psi | 90% | 3297 fps | 100% |
| Norma URP | <<locked>> | 84% | 56,463 psi | 88% | 3182 fps | 100% |
| Ramshot Grand | <<locked>> | 92% | 56,478 psi | 89% | 3284 fps | 99.6% |
| Ramshot Hunter | <<locked>> | 84% | 55,506 psi | 87% | 3192 fps | 100% |
| Ramshot Magnum | <<locked>> | 94% | 54,926 psi | 86% | 3205 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,174 psi | 60% | 2087 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 82% | 54,621 psi | 86% | 3169 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 84% | 56,971 psi | 89% | 3258 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 96% | 54,810 psi | 86% | 3327 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 54,114 psi | 85% | 3274 fps | 98.5% |
| Rottweil R 904 | <<locked>> | 88% | 56,333 psi | 88% | 3176 fps | 99.2% |
| Rottweil R 905 | <<locked>> | 88% | 54,650 psi | 86% | 3189 fps | 99.7% |
| Rottweil R 907 | <<locked>> | 82% | 56,188 psi | 88% | 3146 fps | 99.9% |
| Shooters World Long Rifle | <<locked>> | 82% | 54,955 psi | 86% | 3110 fps | 100% |
| Shooters World SW4350 | <<locked>> | 84% | 56,739 psi | 89% | 3163 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 57,609 psi | 90% | 3117 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 54,244 psi | 85% | 3182 fps | 99.6% |
| Somchem S361 | <<locked>> | 86% | 54,157 psi | 85% | 3104 fps | 98.5% |
| Somchem S365 | <<locked>> | 86% | 57,450 psi | 90% | 3186 fps | 100% |
| Somchem S385 | <<locked>> | 88% | 54,969 psi | 86% | 3156 fps | 99.9% |
| Vihtavuori N160 | <<locked>> | 82% | 54,346 psi | 85% | 3114 fps | 100% |
| Vihtavuori N165 | <<locked>> | 92% | 54,853 psi | 86% | 3136 fps | 99.8% |
| Vihtavuori N550 | <<locked>> | 84% | 57,290 psi | 90% | 3176 fps | 100% |
| Vihtavuori N555 | <<locked>> | 90% | 57,305 psi | 90% | 3212 fps | 100% |
| Vihtavuori N560 | <<locked>> | 90% | 57,087 psi | 89% | 3294 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 94% | 53,838 psi | 84% | 3212 fps | 98.8% |
| Vihtavuori N568 | <<locked>> | 98% | 54,781 psi | 86% | 3278 fps | 98.1% |
| Vihtavuori N570ᴾ | <<locked>> | 100% | 55,709 psi | 87% | 3340 fps | 96.6% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 53,809 psi | 84% | 3064 fps | 100% |
| Winchester 760 | <<locked>> | 82% | 56,101 psi | 88% | 3205 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 92% | 54,056 psi | 85% | 3271 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 54,868 psi | 86% | 3150 fps | 99.6% |
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 3100 | <<locked>> | 80% | 38,319 psi | 60% | 2815 fps | 98.8% |
| Accurate 4350 | <<locked>> | 80% | 50,850 psi | 80% | 3084 fps | 100% |
| Accurate High Country | <<locked>> | 80% | 41,829 psi | 66% | 3002 fps | 96.5% |
| Accurate MAGPRO | <<locked>> | 82% | 42,438 psi | 67% | 3002 fps | 95.3% |
| ADI AR 2209 | <<locked>> | 80% | 42,264 psi | 66% | 2953 fps | 97.6% |
| ADI AR 2213 | <<locked>> | 82% | 40,596 psi | 64% | 2946 fps | 95.9% |
| ADI AR 2217 | <<locked>> | 90% | 39,407 psi | 62% | 2910 fps | 95.9% |
| ADI AR 2225 | <<locked>> | 86% | 31,285 psi | 49% | 2736 fps | 95.6% |
| Alliant Reloder-16 | <<locked>> | 80% | 48,733 psi | 76% | 3094 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 42,279 psi | 66% | 2946 fps | 97.6% |
| Alliant Reloder-22 | <<locked>> | 80% | 38,203 psi | 60% | 2884 fps | 96.5% |
| Alliant Reloder-23 | <<locked>> | 80% | 36,956 psi | 58% | 2841 fps | 100% |
| Alliant Reloder-25 | 56.1 gr | 80% | 31,923 psi | 50% | 2749 fps | 97.7% |
| Alliant Reloder-26 | <<locked>> | 80% | 41,321 psi | 65% | 3009 fps | 99.9% |
| Alliant Reloder-33 | <<locked>> | 98% | 48,805 psi | 76% | 3182 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 48,211 psi | 76% | 3045 fps | 95.1% |
| Bofors RP15 | <<locked>> | 80% | 35,563 psi | 56% | 2815 fps | 95.4% |
| Bofors RP30 | <<locked>> | 86% | 36,318 psi | 57% | 2861 fps | 95% |
| Bofors RP5 | <<locked>> | 80% | 38,203 psi | 60% | 2884 fps | 96.5% |
| Bofors RP7 | <<locked>> | 80% | 52,721 psi | 83% | 3087 fps | 99.8% |
| Hodgdon H1000 | <<locked>> | 86% | 37,637 psi | 59% | 2871 fps | 95.9% |
| Hodgdon H414 | <<locked>> | 80% | 52,344 psi | 82% | 3143 fps | 99.9% |
| Hodgdon H4831 | <<locked>> | 80% | 40,335 psi | 63% | 2884 fps | 95.1% |
| Hodgdon H4831 SC | <<locked>> | 82% | 42,511 psi | 67% | 2933 fps | 95.8% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 45,847 psi | 72% | 2959 fps | 100% |
| Hodgdon Retumbo | 58.2 gr | 82% | 33,460 psi | 52% | 2841 fps | 95.2% |
| Hodgdon Superformance | <<locked>> | 80% | 52,765 psi | 83% | 3173 fps | 99.9% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,963 psi | 44% | 1827 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 48,008 psi | 75% | 3012 fps | 99.4% |
| IMR 4451 Enduron | <<locked>> | 80% | 54,114 psi | 85% | 3110 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 48,269 psi | 76% | 3025 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 41,771 psi | 65% | 2884 fps | 95.8% |
| IMR 7828 SSC | <<locked>> | 82% | 39,131 psi | 61% | 2920 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 94% | 37,043 psi | 58% | 2900 fps | 95.1% |
| Lovex S065 | <<locked>> | 80% | 51,619 psi | 81% | 3054 fps | 100% |
| Lovex S070 | <<locked>> | 80% | 49,995 psi | 78% | 3048 fps | 99.8% |
| Lovex S071 | <<locked>> | 80% | 33,069 psi | 52% | 2680 fps | 97.3% |
| Norma 204 | <<locked>> | 80% | 48,617 psi | 76% | 3064 fps | 98.8% |
| Norma 217 | <<locked>> | 90% | 32,416 psi | 51% | 2795 fps | 95.6% |
| Norma MRP | <<locked>> | 80% | 40,364 psi | 63% | 2963 fps | 98.4% |
| Norma URP | <<locked>> | 80% | 49,545 psi | 78% | 3068 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 39,015 psi | 61% | 2930 fps | 95.9% |
| Ramshot Hunter | <<locked>> | 80% | 48,588 psi | 76% | 3068 fps | 99.9% |
| Ramshot Magnum | <<locked>> | 80% | 32,430 psi | 51% | 2726 fps | 95.2% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,718 psi | 45% | 1873 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 50,952 psi | 80% | 3107 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 49,269 psi | 77% | 3130 fps | 100% |
| ReloadSwiss RS 76 | 62.2 gr | 82% | 32,547 psi | 51% | 2808 fps | 96.2% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 42,859 psi | 67% | 3048 fps | 95.7% |
| Rottweil R 904 | <<locked>> | 80% | 43,381 psi | 68% | 2930 fps | 96.9% |
| Rottweil R 905 | <<locked>> | 80% | 41,771 psi | 65% | 2933 fps | 97.7% |
| Rottweil R 907 | <<locked>> | 80% | 52,721 psi | 83% | 3087 fps | 99.8% |
| Shooters World Long Rifle | <<locked>> | 80% | 51,619 psi | 81% | 3054 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 49,995 psi | 78% | 3048 fps | 99.8% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 50,647 psi | 79% | 3002 fps | 99.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 41,423 psi | 65% | 2930 fps | 97.6% |
| Somchem S361 | <<locked>> | 80% | 44,338 psi | 69% | 2917 fps | 96.4% |
| Somchem S365 | <<locked>> | 80% | 46,891 psi | 73% | 3018 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 42,235 psi | 66% | 2910 fps | 98.4% |
| Vihtavuori N160 | <<locked>> | 80% | 50,937 psi | 80% | 3058 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 36,724 psi | 58% | 2772 fps | 96.7% |
| Vihtavuori N550 | <<locked>> | 80% | 50,473 psi | 79% | 3068 fps | 100% |
| Vihtavuori N555 | <<locked>> | 80% | 41,278 psi | 65% | 2927 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 40,321 psi | 63% | 2953 fps | 95.3% |
| Vihtavuori N565 | <<locked>> | 86% | 40,915 psi | 64% | 2946 fps | 95.8% |
| Vihtavuori N568 | <<locked>> | 92% | 44,179 psi | 69% | 3068 fps | 95.5% |
| Vihtavuori N570 | <<locked>> | 98% | 51,735 psi | 81% | 3264 fps | 95.6% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 50,285 psi | 79% | 3009 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 52,605 psi | 82% | 3146 fps | 99.9% |
| Winchester StaBALL HD | <<locked>> | 80% | 33,837 psi | 53% | 2881 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 38,769 psi | 61% | 2831 fps | 96.7% |
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 77 powders for .257 Weath. Mag. loaded with the .257 | 115gr | Nosler Partition. Vihtavuori N570 delivers the highest muzzle velocity at 3,340 fps; across all powders the maximum-charge window runs from 2,041 fps to 3,340 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 59–90 %, leaving at least 10 % headroom. The 115.0 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 2218, ADI AR 2225 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, Hodgdon Retumbo, ReloadSwiss RS 76 rank at the top here: for .257 Weath. Mag. with the .257 | 115gr | Nosler Partition they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, ADI AR 2218, Alliant Reloder-50, IMR 7977 Enduron 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.