Load Specifications
Load data in caliber .257 Weath. Mag. with .257 | 117gr | Sierra GameKing bullet and 66 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Hodgdon Retumbo, ReloadSwiss RS 76 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>> | 90% | 55,332 psi | 87% | 3117 fps | 100% |
| Accurate 4350 | <<locked>> | 82% | 55,912 psi | 88% | 3146 fps | 100% |
| Accurate MAGPRO | <<locked>> | 90% | 54,839 psi | 86% | 3228 fps | 98.1% |
| ADI AR 2209 | <<locked>> | 88% | 56,739 psi | 89% | 3212 fps | 99.8% |
| ADI AR 2213 | <<locked>> | 90% | 54,926 psi | 86% | 3225 fps | 99.3% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 56,884 psi | 89% | 3248 fps | 99.7% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 51,445 psi | 81% | 3209 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 84% | 56,782 psi | 89% | 3202 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 88% | 56,434 psi | 88% | 3202 fps | 99.8% |
| Alliant Reloder-22 | <<locked>> | 90% | 55,303 psi | 87% | 3219 fps | 99.8% |
| Alliant Reloder-23 | <<locked>> | 92% | 56,913 psi | 89% | 3182 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 96% | 56,768 psi | 89% | 3255 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 88% | 57,740 psi | 90% | 3278 fps | 100% |
| Alliant Reloder-33ᴾ | <<locked>> | 100% | 54,592 psi | 86% | 3274 fps | 97% |
| Baschieri & Pellagri 109 | <<locked>> | 92% | 55,941 psi | 88% | 3176 fps | 97.4% |
| Bofors RP15 | <<locked>> | 92% | 54,520 psi | 85% | 3205 fps | 99.7% |
| Bofors RP30 | <<locked>> | 98% | 56,565 psi | 89% | 3261 fps | 99.7% |
| Bofors RP5 | <<locked>> | 90% | 55,303 psi | 87% | 3219 fps | 99.8% |
| Bofors RP7 | <<locked>> | 82% | 57,261 psi | 90% | 3143 fps | 100% |
| Hodgdon H1000 | <<locked>> | 98% | 54,621 psi | 86% | 3209 fps | 99.8% |
| Hodgdon H4350 | <<locked>> | 82% | 54,592 psi | 86% | 3133 fps | 99.8% |
| Hodgdon H4831 | <<locked>> | 94% | 57,667 psi | 90% | 3209 fps | 99.1% |
| Hodgdon H4831 SC | <<locked>> | 90% | 57,116 psi | 90% | 3199 fps | 99.1% |
| Hodgdon Hybrid 100V | <<locked>> | 86% | 57,000 psi | 89% | 3117 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 55,492 psi | 87% | 3337 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,362 psi | 59% | 2028 fps | 100% |
| IMR 4350 | <<locked>> | 84% | 55,811 psi | 87% | 3130 fps | 100% |
| IMR 4831 | <<locked>> | 88% | 57,696 psi | 90% | 3156 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 88% | 55,071 psi | 86% | 3130 fps | 98.9% |
| IMR 7828 SSC | <<locked>> | 90% | 56,942 psi | 89% | 3264 fps | 99.5% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 47,065 psi | 74% | 3110 fps | 98.4% |
| Lovex S065 | <<locked>> | 82% | 56,014 psi | 88% | 3107 fps | 100% |
| Lovex S070 | <<locked>> | 82% | 54,346 psi | 85% | 3104 fps | 100% |
| Lovex S071 | <<locked>> | 96% | 56,666 psi | 89% | 3140 fps | 100% |
| Norma 204 | <<locked>> | 84% | 57,043 psi | 89% | 3196 fps | 99.8% |
| Norma 217ᴾ | <<locked>> | 100% | 47,529 psi | 74% | 3136 fps | 99.8% |
| Norma MRP | <<locked>> | 88% | 55,303 psi | 87% | 3238 fps | 100% |
| Norma URP | <<locked>> | 82% | 54,056 psi | 85% | 3123 fps | 100% |
| Ramshot Grand | <<locked>> | 88% | 57,000 psi | 89% | 3271 fps | 99.7% |
| Ramshot Hunter | <<locked>> | 84% | 56,855 psi | 89% | 3192 fps | 100% |
| Ramshot Magnum | <<locked>> | 90% | 54,201 psi | 85% | 3173 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,348 psi | 60% | 2077 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 82% | 56,101 psi | 88% | 3169 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 82% | 54,491 psi | 85% | 3199 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 96% | 56,666 psi | 89% | 3333 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 55,927 psi | 88% | 3284 fps | 98.9% |
| Rottweil R 904 | <<locked>> | 88% | 57,624 psi | 90% | 3182 fps | 99.5% |
| Rottweil R 905 | <<locked>> | 88% | 56,043 psi | 88% | 3192 fps | 99.9% |
| Rottweil R 907 | <<locked>> | 82% | 57,261 psi | 90% | 3143 fps | 100% |
| Shooters World Long Rifle | <<locked>> | 82% | 56,014 psi | 88% | 3107 fps | 100% |
| Shooters World SW4350 | <<locked>> | 82% | 54,346 psi | 85% | 3104 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 82% | 55,027 psi | 86% | 3058 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 55,637 psi | 87% | 3186 fps | 99.8% |
| Somchem S361 | <<locked>> | 86% | 55,361 psi | 87% | 3107 fps | 98.8% |
| Somchem S365 | <<locked>> | 84% | 55,259 psi | 87% | 3130 fps | 100% |
| Somchem S385 | <<locked>> | 88% | 56,318 psi | 88% | 3156 fps | 100% |
| Vihtavuori N150 | <<locked>> | 84% | 56,884 psi | 89% | 3058 fps | 100% |
| Vihtavuori N165 | <<locked>> | 92% | 54,418 psi | 85% | 3110 fps | 99.9% |
| Vihtavuori N555 | <<locked>> | 88% | 55,158 psi | 86% | 3156 fps | 100% |
| Vihtavuori N560 | <<locked>> | 90% | 55,651 psi | 87% | 3251 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 94% | 55,506 psi | 87% | 3222 fps | 99.2% |
| Vihtavuori N568 | <<locked>> | 98% | 56,550 psi | 89% | 3287 fps | 98.6% |
| Vihtavuori N570 | <<locked>> | 98% | 54,186 psi | 85% | 3284 fps | 96.5% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 55,114 psi | 86% | 3061 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 92% | 56,260 psi | 88% | 3278 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 53,882 psi | 84% | 3114 fps | 99.7% |
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% | 39,494 psi | 62% | 2822 fps | 99.2% |
| Accurate 4350 | <<locked>> | 80% | 52,286 psi | 82% | 3087 fps | 100% |
| Accurate MAGPRO | <<locked>> | 84% | 44,396 psi | 70% | 3018 fps | 95.5% |
| ADI AR 2209 | <<locked>> | 80% | 43,265 psi | 68% | 2956 fps | 98.1% |
| ADI AR 2213 | <<locked>> | 80% | 38,841 psi | 61% | 2884 fps | 95.6% |
| ADI AR 2217 | <<locked>> | 88% | 37,855 psi | 59% | 2854 fps | 95.6% |
| ADI AR 2225 | <<locked>> | 84% | 30,052 psi | 47% | 2680 fps | 95.3% |
| Alliant Reloder-16 | <<locked>> | 80% | 49,922 psi | 78% | 3091 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 43,482 psi | 68% | 2956 fps | 98.2% |
| Alliant Reloder-22 | <<locked>> | 80% | 39,378 psi | 62% | 2894 fps | 97.2% |
| Alliant Reloder-23 | <<locked>> | 80% | 38,029 psi | 60% | 2844 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 32,808 psi | 51% | 2756 fps | 98.3% |
| Alliant Reloder-26 | <<locked>> | 80% | 42,525 psi | 67% | 3012 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 98% | 50,415 psi | 79% | 3196 fps | 96% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 49,385 psi | 77% | 3051 fps | 95.8% |
| Bofors RP15 | <<locked>> | 80% | 36,535 psi | 57% | 2822 fps | 96% |
| Bofors RP30 | <<locked>> | 86% | 37,391 psi | 59% | 2871 fps | 95.7% |
| Bofors RP5 | <<locked>> | 80% | 39,378 psi | 62% | 2894 fps | 97.2% |
| Bofors RP7 | <<locked>> | 80% | 53,766 psi | 84% | 3084 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 86% | 36,361 psi | 57% | 2818 fps | 95.7% |
| Hodgdon H4350 | <<locked>> | 80% | 51,256 psi | 80% | 3074 fps | 99.5% |
| Hodgdon H4831 | <<locked>> | 84% | 41,669 psi | 65% | 2897 fps | 95.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 40,698 psi | 64% | 2874 fps | 95.5% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 46,963 psi | 74% | 2959 fps | 100% |
| Hodgdon Retumbo | 58.8 gr | 82% | 34,360 psi | 54% | 2854 fps | 96.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,021 psi | 44% | 1818 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 49,023 psi | 77% | 3012 fps | 99.6% |
| IMR 4831 | <<locked>> | 80% | 44,773 psi | 70% | 2936 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 42,656 psi | 67% | 2887 fps | 96.4% |
| IMR 7828 SSC | <<locked>> | 80% | 39,914 psi | 63% | 2923 fps | 96% |
| IMR 8133 Enduron | <<locked>> | 94% | 38,247 psi | 60% | 2910 fps | 95.9% |
| Lovex S065 | <<locked>> | 80% | 52,634 psi | 82% | 3051 fps | 100% |
| Lovex S070 | <<locked>> | 80% | 51,010 psi | 80% | 3048 fps | 99.9% |
| Lovex S071 | <<locked>> | 80% | 34,026 psi | 53% | 2690 fps | 97.9% |
| Norma 204 | <<locked>> | 80% | 49,647 psi | 78% | 3064 fps | 99.1% |
| Norma 217 | <<locked>> | 88% | 31,314 psi | 49% | 2743 fps | 95.3% |
| Norma MRP | <<locked>> | 80% | 41,481 psi | 65% | 2969 fps | 98.9% |
| Norma URP | <<locked>> | 80% | 50,647 psi | 79% | 3064 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 41,872 psi | 66% | 2979 fps | 97.1% |
| Ramshot Hunter | <<locked>> | 80% | 49,647 psi | 78% | 3068 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 36,622 psi | 57% | 2822 fps | 97.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,761 psi | 45% | 1864 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 52,359 psi | 82% | 3110 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 50,705 psi | 79% | 3133 fps | 100% |
| ReloadSwiss RS 76 | 61.4 gr | 80% | 31,241 psi | 49% | 2749 fps | 95.8% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 41,046 psi | 64% | 2989 fps | 95.4% |
| Rottweil R 904 | <<locked>> | 80% | 44,367 psi | 70% | 2933 fps | 97.4% |
| Rottweil R 905 | <<locked>> | 80% | 42,830 psi | 67% | 2940 fps | 98.1% |
| Rottweil R 907 | <<locked>> | 80% | 53,766 psi | 84% | 3084 fps | 99.9% |
| Shooters World Long Rifle | <<locked>> | 80% | 52,634 psi | 82% | 3051 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 51,010 psi | 80% | 3048 fps | 99.9% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 51,634 psi | 81% | 2999 fps | 99.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 42,482 psi | 67% | 2933 fps | 98% |
| Somchem S361 | <<locked>> | 80% | 45,382 psi | 71% | 2923 fps | 97% |
| Somchem S365 | <<locked>> | 80% | 48,138 psi | 75% | 3015 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 43,424 psi | 68% | 2917 fps | 98.9% |
| Vihtavuori N150 | <<locked>> | 80% | 50,270 psi | 79% | 2956 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 36,608 psi | 57% | 2753 fps | 96.9% |
| Vihtavuori N555 | <<locked>> | 80% | 42,395 psi | 66% | 2930 fps | 100% |
| Vihtavuori N560 | 58.3 gr | 80% | 39,407 psi | 62% | 2913 fps | 95.2% |
| Vihtavuori N565 | <<locked>> | 84% | 39,262 psi | 62% | 2890 fps | 95.5% |
| Vihtavuori N568 | <<locked>> | 90% | 42,322 psi | 66% | 3005 fps | 95.2% |
| Vihtavuori N570 | <<locked>> | 96% | 50,314 psi | 79% | 3209 fps | 95.5% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 51,517 psi | 81% | 3005 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 80% | 35,157 psi | 55% | 2887 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 43,468 psi | 68% | 2917 fps | 98.2% |
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 66 powders for .257 Weath. Mag. loaded with the .257 | 117gr | Sierra GameKing. Hodgdon Retumbo delivers the highest muzzle velocity at 3,337 fps; across all powders the maximum-charge window runs from 2,028 fps to 3,337 fps. ADI AR 2217 gives the best case fill at 100 %, and 66 of the 66 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 117.0 gr projectile in 0.257" calls for a 1:10.5 twist; slower twists will usually not stabilise this weight. ADI AR 2217, ADI AR 2225, Alliant Reloder-33 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. Hodgdon Retumbo, ReloadSwiss RS 76, Vihtavuori N560 rank at the top here: for .257 Weath. Mag. with the .257 | 117gr | Sierra GameKing 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.