Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 107gr | Hammer HBC bullet and 73 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Accurate MAGPRO, Accurate High Country 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% | 56,347 psi | 88% | 3248 fps | 100% |
| Accurate 4350 | <<locked>> | 86% | 57,334 psi | 90% | 3287 fps | 100% |
| Accurate High Country | <<locked>> | 92% | 57,740 psi | 90% | 3415 fps | 99% |
| Accurate MAGPRO | <<locked>> | 92% | 54,984 psi | 86% | 3346 fps | 97.6% |
| ADI AR 2209 | <<locked>> | 90% | 54,418 psi | 85% | 3284 fps | 99.1% |
| ADI AR 2213 | <<locked>> | 94% | 56,115 psi | 88% | 3353 fps | 98.7% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 50,299 psi | 79% | 3232 fps | 98% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 44,918 psi | 70% | 3182 fps | 99.4% |
| Alliant Reloder-16 | <<locked>> | 86% | 54,302 psi | 85% | 3291 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 82% | 55,521 psi | 87% | 3304 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 92% | 57,667 psi | 90% | 3337 fps | 99.5% |
| Alliant Reloder-22 | <<locked>> | 94% | 56,188 psi | 88% | 3350 fps | 99.5% |
| Alliant Reloder-23 | <<locked>> | 96% | 57,319 psi | 90% | 3317 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 56,826 psi | 89% | 3379 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 90% | 53,809 psi | 84% | 3346 fps | 100% |
| Bofors RP15 | <<locked>> | 96% | 55,085 psi | 86% | 3327 fps | 99.3% |
| Bofors RP30ᴾ | <<locked>> | 100% | 52,866 psi | 83% | 3314 fps | 98.7% |
| Bofors RP5 | <<locked>> | 94% | 56,188 psi | 88% | 3350 fps | 99.5% |
| Bofors RP7 | <<locked>> | 84% | 55,622 psi | 87% | 3225 fps | 99.7% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 55,492 psi | 87% | 3330 fps | 99.3% |
| Hodgdon H414 | <<locked>> | 84% | 55,129 psi | 86% | 3284 fps | 99.9% |
| Hodgdon H4350 | <<locked>> | 84% | 57,609 psi | 90% | 3297 fps | 99.6% |
| Hodgdon H4831 | <<locked>> | 92% | 55,912 psi | 88% | 3281 fps | 98% |
| Hodgdon H4831 SC | <<locked>> | 92% | 54,810 psi | 86% | 3264 fps | 97.9% |
| Hodgdon Hybrid 100V | <<locked>> | 88% | 54,766 psi | 86% | 3205 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 55,564 psi | 87% | 3461 fps | 99.9% |
| Hodgdon Superformance | <<locked>> | 84% | 55,854 psi | 88% | 3323 fps | 99.8% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,130 psi | 58% | 2093 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 57,435 psi | 90% | 3271 fps | 99.8% |
| IMR 4451 Enduron | <<locked>> | 84% | 57,116 psi | 90% | 3251 fps | 99.9% |
| IMR 4831 | <<locked>> | 88% | 57,667 psi | 90% | 3278 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 56,681 psi | 89% | 3264 fps | 98.3% |
| IMR 7828 SSC | <<locked>> | 96% | 57,711 psi | 90% | 3392 fps | 99% |
| Lovex S065 | <<locked>> | 84% | 54,520 psi | 85% | 3196 fps | 100% |
| Lovex S070 | <<locked>> | 86% | 55,985 psi | 88% | 3245 fps | 99.9% |
| Lovex S071ᴾ | <<locked>> | 100% | 57,188 psi | 90% | 3261 fps | 100% |
| Norma 204 | <<locked>> | 86% | 54,926 psi | 86% | 3268 fps | 99.1% |
| Norma 217ᴾ | <<locked>> | 100% | 40,567 psi | 64% | 3100 fps | 97.8% |
| Norma MRP | <<locked>> | 92% | 55,941 psi | 88% | 3369 fps | 99.9% |
| Norma URP | <<locked>> | 86% | 55,448 psi | 87% | 3268 fps | 100% |
| Ramshot Grand | <<locked>> | 94% | 54,592 psi | 86% | 3346 fps | 98.8% |
| Ramshot Hunter | <<locked>> | 86% | 54,520 psi | 85% | 3271 fps | 100% |
| Ramshot Magnum | <<locked>> | 98% | 57,232 psi | 90% | 3340 fps | 99.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,840 psi | 59% | 2142 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 57,392 psi | 90% | 3310 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 86% | 55,680 psi | 87% | 3340 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 56,913 psi | 89% | 3458 fps | 100% |
| ReloadSwiss RS 80ᴾ | <<locked>> | 100% | 51,793 psi | 81% | 3327 fps | 97.3% |
| Rottweil R 903 | <<locked>> | 82% | 57,043 psi | 89% | 3228 fps | 100% |
| Rottweil R 904 | <<locked>> | 90% | 55,419 psi | 87% | 3248 fps | 98.5% |
| Rottweil R 905 | <<locked>> | 92% | 57,116 psi | 90% | 3323 fps | 99.5% |
| Rottweil R 907 | <<locked>> | 84% | 55,622 psi | 87% | 3225 fps | 99.7% |
| Shooters World Long Rifle | <<locked>> | 84% | 54,520 psi | 85% | 3196 fps | 100% |
| Shooters World SW4350 | <<locked>> | 86% | 55,985 psi | 88% | 3245 fps | 99.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 56,753 psi | 89% | 3087 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 57,188 psi | 90% | 3199 fps | 99.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 92% | 56,681 psi | 89% | 3317 fps | 99.5% |
| Somchem S355 | <<locked>> | 82% | 56,652 psi | 89% | 3222 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 57,188 psi | 90% | 3238 fps | 98.2% |
| Somchem S365 | <<locked>> | 88% | 56,115 psi | 88% | 3271 fps | 100% |
| Somchem S385 | <<locked>> | 90% | 54,070 psi | 85% | 3232 fps | 99.6% |
| Vihtavuori N150 | <<locked>> | 82% | 54,360 psi | 85% | 3133 fps | 100% |
| Vihtavuori N160 | <<locked>> | 86% | 57,392 psi | 90% | 3258 fps | 100% |
| Vihtavuori N165 | <<locked>> | 96% | 57,261 psi | 90% | 3264 fps | 99.7% |
| Vihtavuori N550 | <<locked>> | 86% | 56,695 psi | 89% | 3264 fps | 100% |
| Vihtavuori N555 | <<locked>> | 92% | 55,941 psi | 88% | 3291 fps | 100% |
| Vihtavuori N560 | <<locked>> | 92% | 55,680 psi | 87% | 3360 fps | 98.3% |
| Vihtavuori N565 | <<locked>> | 98% | 55,782 psi | 87% | 3337 fps | 98.5% |
| Vihtavuori N568ᴾ | <<locked>> | 100% | 52,605 psi | 82% | 3330 fps | 96.8% |
| Winchester 6.5 StaBALL | <<locked>> | 86% | 57,188 psi | 90% | 3209 fps | 100% |
| Winchester 760 | <<locked>> | 84% | 55,376 psi | 87% | 3287 fps | 99.9% |
| Winchester StaBALL HD | <<locked>> | 96% | 55,521 psi | 87% | 3406 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 92% | 53,853 psi | 84% | 3219 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% | 34,867 psi | 55% | 2812 fps | 97.1% |
| Accurate 4350 | <<locked>> | 80% | 46,673 psi | 73% | 3104 fps | 100% |
| Accurate High Country | 58.6 gr | 82% | 40,596 psi | 64% | 3061 fps | 95% |
| Accurate MAGPRO | 64 gr | 88% | 47,427 psi | 74% | 3199 fps | 95.8% |
| ADI AR 2209 | <<locked>> | 80% | 38,827 psi | 61% | 2953 fps | 95.6% |
| ADI AR 2213 | <<locked>> | 86% | 42,496 psi | 67% | 3071 fps | 95.4% |
| ADI AR 2217 | <<locked>> | 94% | 41,147 psi | 64% | 3028 fps | 95.3% |
| ADI AR 2225 | <<locked>> | 92% | 34,476 psi | 54% | 2910 fps | 96.1% |
| Alliant Reloder-16 | <<locked>> | 80% | 44,425 psi | 70% | 3107 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 80% | 51,779 psi | 81% | 3245 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 38,885 psi | 61% | 2949 fps | 95.6% |
| Alliant Reloder-22 | <<locked>> | 82% | 37,260 psi | 58% | 2949 fps | 95.2% |
| Alliant Reloder-23 | <<locked>> | 80% | 33,388 psi | 52% | 2844 fps | 99.4% |
| Alliant Reloder-25 | <<locked>> | 80% | 29,109 psi | 46% | 2733 fps | 95.1% |
| Alliant Reloder-26 | 58.9 gr | 80% | 36,738 psi | 58% | 2995 fps | 98.9% |
| Bofors RP15 | <<locked>> | 86% | 39,465 psi | 62% | 3002 fps | 95.9% |
| Bofors RP30 | <<locked>> | 92% | 40,001 psi | 63% | 3041 fps | 95.4% |
| Bofors RP5 | <<locked>> | 82% | 37,260 psi | 58% | 2949 fps | 95.2% |
| Bofors RP7 | <<locked>> | 80% | 49,211 psi | 77% | 3110 fps | 99% |
| Hodgdon H1000 | <<locked>> | 90% | 39,218 psi | 61% | 2986 fps | 95.3% |
| Hodgdon H414 | <<locked>> | 80% | 48,196 psi | 76% | 3156 fps | 99.2% |
| Hodgdon H4350 | <<locked>> | 80% | 50,734 psi | 80% | 3176 fps | 98.8% |
| Hodgdon H4831 | <<locked>> | 86% | 45,455 psi | 71% | 3081 fps | 95.7% |
| Hodgdon H4831 SC | <<locked>> | 86% | 44,556 psi | 70% | 3061 fps | 95.4% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 42,032 psi | 66% | 2979 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 37,086 psi | 58% | 3028 fps | 95.8% |
| Hodgdon Superformance | <<locked>> | 80% | 47,950 psi | 75% | 3176 fps | 99.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,818 psi | 44% | 1877 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 44,628 psi | 70% | 3028 fps | 98.3% |
| IMR 4451 Enduron | <<locked>> | 80% | 50,401 psi | 79% | 3133 fps | 99.4% |
| IMR 4831 | <<locked>> | 80% | 44,251 psi | 69% | 3041 fps | 99.9% |
| IMR 4955 Enduron | <<locked>> | 84% | 44,048 psi | 69% | 3015 fps | 95.5% |
| IMR 7828 SSC | <<locked>> | 88% | 43,772 psi | 69% | 3117 fps | 96% |
| Lovex S065 | <<locked>> | 80% | 48,066 psi | 75% | 3081 fps | 99.8% |
| Lovex S070 | <<locked>> | 80% | 46,412 psi | 73% | 3064 fps | 99.1% |
| Lovex S071 | <<locked>> | 80% | 29,950 psi | 47% | 2674 fps | 95% |
| Norma 204 | <<locked>> | 80% | 44,759 psi | 70% | 3071 fps | 97.2% |
| Norma 217 | <<locked>> | 96% | 35,375 psi | 55% | 2963 fps | 95.8% |
| Norma MRP | <<locked>> | 80% | 36,419 psi | 57% | 2956 fps | 96.4% |
| Norma URP | <<locked>> | 80% | 45,658 psi | 72% | 3087 fps | 99.9% |
| Ramshot Grand | <<locked>> | 86% | 40,611 psi | 64% | 3051 fps | 95.3% |
| Ramshot Hunter | <<locked>> | 80% | 44,599 psi | 70% | 3081 fps | 99.2% |
| Ramshot Magnum | <<locked>> | 86% | 36,303 psi | 57% | 2913 fps | 95.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,326 psi | 44% | 1919 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 46,630 psi | 73% | 3123 fps | 99.9% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 44,672 psi | 70% | 3136 fps | 99.8% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 34,011 psi | 53% | 2930 fps | 95.6% |
| ReloadSwiss RS 80 | <<locked>> | 96% | 44,266 psi | 69% | 3169 fps | 95.1% |
| Rottweil R 903 | <<locked>> | 80% | 53,606 psi | 84% | 3173 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 42,772 psi | 67% | 2995 fps | 95.7% |
| Rottweil R 905 | <<locked>> | 80% | 38,232 psi | 60% | 2933 fps | 95.6% |
| Rottweil R 907 | <<locked>> | 80% | 49,211 psi | 77% | 3110 fps | 99% |
| Shooters World Long Rifle | <<locked>> | 80% | 48,066 psi | 75% | 3081 fps | 99.8% |
| Shooters World SW4350 | <<locked>> | 80% | 46,412 psi | 73% | 3064 fps | 99.1% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 53,330 psi | 84% | 3038 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 47,065 psi | 74% | 3018 fps | 99.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 37,927 psi | 59% | 2930 fps | 95.5% |
| Somchem S355 | <<locked>> | 80% | 53,272 psi | 83% | 3166 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 43,801 psi | 69% | 2982 fps | 95.2% |
| Somchem S365 | <<locked>> | 80% | 42,699 psi | 67% | 3038 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 38,841 psi | 61% | 2917 fps | 96.7% |
| Vihtavuori N150 | <<locked>> | 80% | 51,082 psi | 80% | 3084 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 47,123 psi | 74% | 3084 fps | 100% |
| Vihtavuori N165 | <<locked>> | 82% | 35,839 psi | 56% | 2831 fps | 95.3% |
| Vihtavuori N550 | <<locked>> | 80% | 46,543 psi | 73% | 3084 fps | 99.9% |
| Vihtavuori N555 | <<locked>> | 80% | 37,463 psi | 59% | 2930 fps | 99.4% |
| Vihtavuori N560 | <<locked>> | 86% | 45,063 psi | 71% | 3150 fps | 95.8% |
| Vihtavuori N565 | <<locked>> | 90% | 42,380 psi | 66% | 3068 fps | 95.3% |
| Vihtavuori N568 | <<locked>> | 98% | 48,979 psi | 77% | 3258 fps | 95.9% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 46,195 psi | 72% | 3031 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 48,443 psi | 76% | 3159 fps | 99.3% |
| Winchester StaBALL HD | <<locked>> | 80% | 29,791 psi | 47% | 2858 fps | 99.6% |
| Winchester Supreme 780 | <<locked>> | 82% | 37,942 psi | 59% | 2894 fps | 95.4% |
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 | 107gr | Hammer HBC. Hodgdon Retumbo delivers the highest muzzle velocity at 3,461 fps; across all powders the maximum-charge window runs from 2,093 fps to 3,461 fps. ADI AR 2217 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 58–90 %, leaving at least 10 % headroom. The 107.0 gr projectile in 0.257" calls for a 1:7.5 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. Accurate MAGPRO, Accurate High Country, Alliant Reloder-26 rank at the top here: for .257 Weath. Mag. with the .257 | 107gr | Hammer HBC they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Alliant Reloder-33, IMR 7977 Enduron, Vihtavuori N170 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.