Load Specifications
Load data in caliber .257 Ackley Improved with .257 | 87gr | Sierra VarmintKing bullet and 86 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-16, Somchem S365 and Hodgdon Hybrid 100V.
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: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 4064 | <<locked>> | 82% | 42,424 psi | 88% | 3071 fps | 99.9% |
| Accurate 4064 | <<locked>> | 82% | 42,235 psi | 88% | 3064 fps | 99.9% |
| Accurate 4064 | <<locked>> | 82% | 42,699 psi | 89% | 3077 fps | 100% |
| Accurate 4350 | <<locked>> | 90% | 41,408 psi | 86% | 3104 fps | 96% |
| Accurate 4350 | <<locked>> | 90% | 41,278 psi | 86% | 3100 fps | 96% |
| Accurate 4350 | <<locked>> | 90% | 41,930 psi | 87% | 3117 fps | 96.2% |
| ADI AR 2208 | <<locked>> | 82% | 40,988 psi | 85% | 3018 fps | 96.5% |
| ADI AR 2208 | <<locked>> | 82% | 41,104 psi | 85% | 3025 fps | 96.5% |
| ADI AR 2208 | <<locked>> | 82% | 41,452 psi | 86% | 3035 fps | 96.7% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 43,381 psi | 90% | 3107 fps | 98.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 43,526 psi | 90% | 3107 fps | 98.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 41,046 psi | 85% | 3054 fps | 98.1% |
| Alliant Reloder-16 | <<locked>> | 92% | 43,497 psi | 90% | 3182 fps | 96.9% |
| Alliant Reloder-16 | <<locked>> | 92% | 43,352 psi | 90% | 3176 fps | 96.8% |
| Alliant Reloder-16 | <<locked>> | 90% | 41,104 psi | 85% | 3127 fps | 96.2% |
| Alliant Reloder-17 | <<locked>> | 88% | 43,598 psi | 90% | 3209 fps | 98.5% |
| Alliant Reloder-17 | <<locked>> | 88% | 43,439 psi | 90% | 3205 fps | 98.4% |
| Alliant Reloder-17 | <<locked>> | 86% | 41,133 psi | 85% | 3153 fps | 97.9% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 40,234 psi | 83% | 3117 fps | 97.6% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 40,161 psi | 83% | 3114 fps | 97.6% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 40,640 psi | 84% | 3130 fps | 97.8% |
| Bofors RP3 | <<locked>> | 82% | 40,727 psi | 84% | 3051 fps | 98.1% |
| Bofors RP3 | <<locked>> | 84% | 43,468 psi | 90% | 3114 fps | 98.7% |
| Bofors RP3 | <<locked>> | 82% | 40,959 psi | 85% | 3058 fps | 98.2% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 42,902 psi | 89% | 3117 fps | 98.2% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 42,728 psi | 89% | 3110 fps | 98.2% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 43,308 psi | 90% | 3127 fps | 98.4% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,375 psi | 73% | 2103 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,433 psi | 74% | 2106 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,302 psi | 73% | 2106 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 43,047 psi | 89% | 3064 fps | 97.3% |
| IMR 4064 | <<locked>> | 82% | 43,178 psi | 90% | 3064 fps | 97.3% |
| IMR 4064 | <<locked>> | 82% | 43,540 psi | 90% | 3077 fps | 97.5% |
| IMR 4831 | <<locked>> | 92% | 42,395 psi | 88% | 3107 fps | 96.5% |
| IMR 4831 | <<locked>> | 92% | 42,279 psi | 88% | 3104 fps | 96.4% |
| IMR 4831 | <<locked>> | 92% | 42,873 psi | 89% | 3117 fps | 96.6% |
| Lovex S062 | <<locked>> | 82% | 43,033 psi | 89% | 3068 fps | 98.8% |
| Lovex S062 | <<locked>> | 82% | 42,873 psi | 89% | 3068 fps | 98.8% |
| Lovex S062 | <<locked>> | 82% | 43,555 psi | 90% | 3084 fps | 98.9% |
| Norma 203B | <<locked>> | 82% | 43,149 psi | 90% | 3110 fps | 97.8% |
| Norma 203B | <<locked>> | 82% | 42,989 psi | 89% | 3104 fps | 97.7% |
| Norma URP | <<locked>> | 90% | 41,582 psi | 86% | 3107 fps | 96% |
| Ramshot Big Game | <<locked>> | 82% | 43,178 psi | 90% | 3123 fps | 97.6% |
| Ramshot Big Game | <<locked>> | 82% | 42,989 psi | 89% | 3120 fps | 97.6% |
| Ramshot Big Game | <<locked>> | 82% | 43,366 psi | 90% | 3130 fps | 97.7% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,708 psi | 74% | 2149 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,781 psi | 74% | 2149 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,897 psi | 74% | 2156 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 43,395 psi | 90% | 3222 fps | 99.8% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 43,236 psi | 90% | 3219 fps | 99.8% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 40,712 psi | 84% | 3159 fps | 99.6% |
| Rottweil R 903 | <<locked>> | 86% | 43,497 psi | 90% | 3107 fps | 98.5% |
| Rottweil R 903 | <<locked>> | 84% | 40,683 psi | 84% | 3045 fps | 97.8% |
| Rottweil R 903 | <<locked>> | 84% | 41,118 psi | 85% | 3058 fps | 98% |
| Shooters World Precision | <<locked>> | 82% | 43,033 psi | 89% | 3068 fps | 98.8% |
| Shooters World Precision | <<locked>> | 82% | 42,873 psi | 89% | 3068 fps | 98.8% |
| Shooters World Precision | <<locked>> | 82% | 43,555 psi | 90% | 3084 fps | 98.9% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 41,974 psi | 87% | 3104 fps | 97.4% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 42,047 psi | 87% | 3104 fps | 97.4% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 42,424 psi | 88% | 3114 fps | 97.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 43,076 psi | 89% | 2992 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 43,221 psi | 90% | 2992 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 43,584 psi | 90% | 3005 fps | 100% |
| Somchem S355 | <<locked>> | 84% | 41,495 psi | 86% | 3054 fps | 97.8% |
| Somchem S355 | <<locked>> | 84% | 41,350 psi | 86% | 3048 fps | 97.8% |
| Somchem S355 | <<locked>> | 84% | 41,727 psi | 87% | 3061 fps | 97.9% |
| Somchem S365 | <<locked>> | 94% | 42,177 psi | 88% | 3169 fps | 99.2% |
| Somchem S365 | <<locked>> | 94% | 42,279 psi | 88% | 3169 fps | 99.2% |
| Somchem S365 | <<locked>> | 94% | 42,641 psi | 88% | 3179 fps | 99.3% |
| Vihtavuori N150 | <<locked>> | 86% | 42,264 psi | 88% | 3038 fps | 99.1% |
| Vihtavuori N150 | <<locked>> | 86% | 42,380 psi | 88% | 3041 fps | 99.1% |
| Vihtavuori N150 | <<locked>> | 86% | 42,699 psi | 89% | 3048 fps | 99.2% |
| Vihtavuori N160 | <<locked>> | 90% | 43,221 psi | 90% | 3104 fps | 96.4% |
| Vihtavuori N160 | <<locked>> | 90% | 43,120 psi | 89% | 3100 fps | 96.3% |
| Vihtavuori N550 | <<locked>> | 90% | 42,511 psi | 88% | 3100 fps | 96% |
| Vihtavuori N550 | <<locked>> | 90% | 42,409 psi | 88% | 3097 fps | 95.9% |
| Vihtavuori N550 | <<locked>> | 90% | 42,946 psi | 89% | 3110 fps | 96.2% |
| Vihtavuori N555 | <<locked>> | 98% | 41,176 psi | 85% | 3140 fps | 96.7% |
| Vihtavuori N555 | <<locked>> | 98% | 41,017 psi | 85% | 3136 fps | 96.7% |
| Vihtavuori N555 | <<locked>> | 98% | 41,626 psi | 86% | 3153 fps | 96.9% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 43,236 psi | 90% | 3077 fps | 98.5% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 43,395 psi | 90% | 3081 fps | 98.6% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 40,843 psi | 85% | 3028 fps | 98.1% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 36,187 psi | 75% | 3094 fps | 97% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 36,071 psi | 75% | 3091 fps | 96.9% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 36,448 psi | 76% | 3107 fps | 97.2% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 4064 | <<locked>> | 80% | 39,595 psi | 82% | 3009 fps | 99.7% |
| Accurate 4064 | <<locked>> | 80% | 39,450 psi | 82% | 3005 fps | 99.7% |
| Accurate 4064 | <<locked>> | 80% | 39,885 psi | 83% | 3015 fps | 99.8% |
| Accurate 4350 | <<locked>> | 88% | 38,522 psi | 80% | 3035 fps | 95% |
| Accurate 4350 | <<locked>> | 88% | 38,392 psi | 80% | 3031 fps | 95% |
| Accurate 4350 | <<locked>> | 88% | 39,015 psi | 81% | 3048 fps | 95.3% |
| ADI AR 2208 | <<locked>> | 80% | 38,537 psi | 80% | 2959 fps | 95.7% |
| ADI AR 2208 | <<locked>> | 80% | 38,406 psi | 80% | 2956 fps | 95.7% |
| ADI AR 2208 | <<locked>> | 80% | 38,769 psi | 80% | 2969 fps | 95.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 38,130 psi | 79% | 2982 fps | 97.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 38,203 psi | 79% | 2982 fps | 97.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 38,595 psi | 80% | 2995 fps | 97.5% |
| Alliant Reloder-16 | 45.1 gr | 88% | 38,290 psi | 79% | 3048 fps | 95% |
| Alliant Reloder-16 | 46.2 gr | 90% | 40,567 psi | 84% | 3107 fps | 95.9% |
| Alliant Reloder-16 | 46.2 gr | 88% | 38,682 psi | 80% | 3061 fps | 95.3% |
| Alliant Reloder-17 | <<locked>> | 82% | 35,375 psi | 73% | 2995 fps | 95.8% |
| Alliant Reloder-17 | <<locked>> | 82% | 35,447 psi | 74% | 2995 fps | 95.8% |
| Alliant Reloder-17 | <<locked>> | 82% | 35,766 psi | 74% | 3009 fps | 96% |
| Alliant Reloder-23 | <<locked>> | 96% | 35,418 psi | 73% | 2986 fps | 95.7% |
| Alliant Reloder-23 | <<locked>> | 96% | 35,346 psi | 73% | 2982 fps | 95.7% |
| Alliant Reloder-23 | <<locked>> | 96% | 35,766 psi | 74% | 2995 fps | 96% |
| Bofors RP3 | <<locked>> | 80% | 37,956 psi | 79% | 2986 fps | 97.4% |
| Bofors RP3 | <<locked>> | 80% | 37,811 psi | 78% | 2982 fps | 97.3% |
| Bofors RP3 | <<locked>> | 80% | 38,203 psi | 79% | 2992 fps | 97.5% |
| Hodgdon Hybrid 100V | 45.8 gr | 88% | 35,273 psi | 73% | 2927 fps | 95.9% |
| Hodgdon Hybrid 100V | 45.8 gr | 88% | 35,128 psi | 73% | 2923 fps | 95.8% |
| Hodgdon Hybrid 100V | 44.8 gr | 86% | 33,286 psi | 69% | 2874 fps | 95.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,310 psi | 55% | 1883 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,353 psi | 55% | 1886 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,310 psi | 55% | 1886 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 40,466 psi | 84% | 3002 fps | 96.6% |
| IMR 4064 | <<locked>> | 80% | 40,321 psi | 84% | 2999 fps | 96.6% |
| IMR 4064 | <<locked>> | 80% | 40,712 psi | 84% | 3012 fps | 96.7% |
| IMR 4831 | <<locked>> | 90% | 39,798 psi | 83% | 3045 fps | 95.6% |
| IMR 4831 | <<locked>> | 90% | 39,682 psi | 82% | 3041 fps | 95.6% |
| IMR 4831 | <<locked>> | 90% | 40,016 psi | 83% | 3054 fps | 95.7% |
| Lovex S062 | <<locked>> | 80% | 40,466 psi | 84% | 3009 fps | 98.3% |
| Lovex S062 | <<locked>> | 80% | 40,321 psi | 84% | 3009 fps | 98.3% |
| Lovex S062 | <<locked>> | 80% | 40,712 psi | 84% | 3018 fps | 98.4% |
| Norma 203B | <<locked>> | 80% | 40,321 psi | 84% | 3041 fps | 97% |
| Norma 203B | <<locked>> | 80% | 40,451 psi | 84% | 3045 fps | 97.1% |
| Norma URP | <<locked>> | 88% | 39,059 psi | 81% | 3048 fps | 95.1% |
| Ramshot Big Game | <<locked>> | 80% | 40,045 psi | 83% | 3051 fps | 96.8% |
| Ramshot Big Game | <<locked>> | 80% | 40,161 psi | 83% | 3054 fps | 96.8% |
| Ramshot Big Game | <<locked>> | 80% | 40,524 psi | 84% | 3064 fps | 97% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,687 psi | 55% | 1929 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,731 psi | 55% | 1932 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,672 psi | 55% | 1932 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 35,186 psi | 73% | 3005 fps | 98.2% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 35,273 psi | 73% | 3009 fps | 98.2% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 35,592 psi | 74% | 3022 fps | 98.4% |
| Rottweil R 903 | <<locked>> | 80% | 35,752 psi | 74% | 2923 fps | 96.4% |
| Rottweil R 903 | <<locked>> | 80% | 35,592 psi | 74% | 2917 fps | 96.3% |
| Rottweil R 903 | <<locked>> | 80% | 35,969 psi | 75% | 2927 fps | 96.5% |
| Shooters World Precision | <<locked>> | 80% | 40,466 psi | 84% | 3009 fps | 98.3% |
| Shooters World Precision | <<locked>> | 80% | 40,321 psi | 84% | 3009 fps | 98.3% |
| Shooters World Precision | <<locked>> | 80% | 40,712 psi | 84% | 3018 fps | 98.4% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 36,622 psi | 76% | 2972 fps | 95.7% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 36,680 psi | 76% | 2972 fps | 95.7% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 37,043 psi | 77% | 2982 fps | 95.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 38,000 psi | 79% | 2884 fps | 99.8% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 37,826 psi | 78% | 2881 fps | 99.8% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 38,232 psi | 79% | 2890 fps | 99.9% |
| Somchem S355 | <<locked>> | 80% | 36,434 psi | 76% | 2930 fps | 96.3% |
| Somchem S355 | <<locked>> | 80% | 36,318 psi | 75% | 2923 fps | 96.3% |
| Somchem S355 | <<locked>> | 80% | 36,695 psi | 76% | 2936 fps | 96.5% |
| Somchem S365 | 45 gr | 84% | 30,197 psi | 63% | 2838 fps | 95.1% |
| Somchem S365 | 45 gr | 84% | 30,284 psi | 63% | 2841 fps | 95.2% |
| Somchem S365 | 45 gr | 84% | 30,560 psi | 63% | 2851 fps | 95.4% |
| Vihtavuori N150 | <<locked>> | 80% | 34,766 psi | 72% | 2858 fps | 97.3% |
| Vihtavuori N150 | <<locked>> | 80% | 34,664 psi | 72% | 2854 fps | 97.2% |
| Vihtavuori N150 | <<locked>> | 80% | 35,012 psi | 73% | 2867 fps | 97.4% |
| Vihtavuori N160 | <<locked>> | 88% | 40,350 psi | 84% | 3041 fps | 95.5% |
| Vihtavuori N160 | <<locked>> | 88% | 40,205 psi | 83% | 3035 fps | 95.4% |
| Vihtavuori N550 | <<locked>> | 88% | 39,784 psi | 83% | 3038 fps | 95.1% |
| Vihtavuori N550 | <<locked>> | 88% | 39,871 psi | 83% | 3038 fps | 95.1% |
| Vihtavuori N550 | <<locked>> | 88% | 40,176 psi | 83% | 3048 fps | 95.3% |
| Vihtavuori N555 | <<locked>> | 96% | 38,609 psi | 80% | 3077 fps | 95.9% |
| Vihtavuori N555 | <<locked>> | 96% | 38,435 psi | 80% | 3074 fps | 95.8% |
| Vihtavuori N555 | <<locked>> | 94% | 36,361 psi | 75% | 3022 fps | 95.1% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 32,996 psi | 68% | 2818 fps | 95.1% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 33,069 psi | 69% | 2818 fps | 95.1% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 33,301 psi | 69% | 2831 fps | 95.4% |
| Winchester StaBALL HD | <<locked>> | 98% | 33,837 psi | 70% | 3015 fps | 95.6% |
| Winchester StaBALL HD | <<locked>> | 98% | 33,750 psi | 70% | 3012 fps | 95.5% |
| Winchester StaBALL HD | <<locked>> | 98% | 34,156 psi | 71% | 3031 fps | 95.9% |
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 86 powders for .257 Ackley Improved loaded with the .257 | 87gr | Sierra VarmintKing. ReloadSwiss RS 60 delivers the highest muzzle velocity at 3,222 fps; across all powders the maximum-charge window runs from 2,103 fps to 3,222 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 86 of the 86 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (332 MPa), the top charges use 73–90 %, leaving at least 10 % headroom. The 87.0 gr projectile in 0.257" calls for a 1:13.5 twist; slower twists will usually not stabilise this weight. Alliant Reloder-23, Alliant Reloder-23, Alliant Reloder-23 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-16, Somchem S365, Hodgdon Hybrid 100V rank at the top here: for .257 Ackley Improved with the .257 | 87gr | Sierra VarmintKing 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.