Load Specifications
Load data in caliber .255 GS with .257 | 95gr | Hammer HHT bullet and 99 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Power Pro 2000-MR, ReloadSwiss RS 60 and Hodgdon Superformance.
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 2015 | <<locked>> | 84% | 54,781 psi | 86% | 3097 fps | 100% |
| Accurate 2460 | <<locked>> | 82% | 57,014 psi | 89% | 3176 fps | 100% |
| Accurate 2495 | <<locked>> | 90% | 57,174 psi | 90% | 3169 fps | 100% |
| Accurate 2520 | <<locked>> | 84% | 55,390 psi | 87% | 3189 fps | 100% |
| Accurate 2700 | <<locked>> | 90% | 56,869 psi | 89% | 3166 fps | 96.6% |
| Accurate 4064 | <<locked>> | 92% | 57,174 psi | 90% | 3219 fps | 100% |
| Accurate 4350 | <<locked>> | 98% | 53,896 psi | 84% | 3248 fps | 99.1% |
| ADI AR 2206H | <<locked>> | 86% | 54,186 psi | 85% | 3199 fps | 99.7% |
| ADI AR 2208 | <<locked>> | 92% | 55,434 psi | 87% | 3199 fps | 99.5% |
| ADI Benchmark 8208 | <<locked>> | 86% | 56,695 psi | 89% | 3209 fps | 100% |
| Alliant AR-Comp | <<locked>> | 84% | 53,998 psi | 85% | 3130 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 88% | 54,215 psi | 85% | 3327 fps | 99.5% |
| Alliant Reloder- TS 15.5 | <<locked>> | 92% | 55,288 psi | 87% | 3222 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 90% | 56,086 psi | 88% | 3248 fps | 99.7% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 55,390 psi | 87% | 3314 fps | 99.6% |
| Alliant Reloder-17 | <<locked>> | 96% | 56,956 psi | 89% | 3356 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 39,320 psi | 62% | 2999 fps | 97.9% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 44,440 psi | 70% | 3179 fps | 97.2% |
| Baschieri & Pellagri 107 | <<locked>> | 86% | 54,346 psi | 85% | 3212 fps | 99.2% |
| Bofors RP3 | <<locked>> | 92% | 56,014 psi | 88% | 3238 fps | 100% |
| Bofors RP7 | <<locked>> | 96% | 56,086 psi | 88% | 3199 fps | 96.7% |
| Hodgdon Benchmark | <<locked>> | 84% | 54,795 psi | 86% | 3133 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 86% | 56,405 psi | 88% | 3235 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 82% | 54,766 psi | 86% | 3284 fps | 99.6% |
| Hodgdon H322 | <<locked>> | 82% | 57,305 psi | 90% | 3202 fps | 100% |
| Hodgdon H380 | <<locked>> | 92% | 57,087 psi | 89% | 3251 fps | 99.1% |
| Hodgdon H414 | <<locked>> | 98% | 57,087 psi | 89% | 3304 fps | 97.6% |
| Hodgdon H4350 | <<locked>> | 96% | 57,624 psi | 90% | 3264 fps | 96.3% |
| Hodgdon H4895 | <<locked>> | 86% | 54,723 psi | 86% | 3212 fps | 99.9% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 51,314 psi | 80% | 3169 fps | 99.7% |
| Hodgdon LEVERevolution | <<locked>> | 88% | 54,636 psi | 86% | 3248 fps | 100% |
| Hodgdon Superformance | <<locked>> | 96% | 54,157 psi | 85% | 3278 fps | 96.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,273 psi | 55% | 2008 fps | 100% |
| Hodgdon VARGET | <<locked>> | 88% | 56,217 psi | 88% | 3219 fps | 99.9% |
| IMR 3031 | <<locked>> | 86% | 54,592 psi | 86% | 3199 fps | 100% |
| IMR 4064 | <<locked>> | 90% | 54,810 psi | 86% | 3182 fps | 99.6% |
| IMR 4166 Enduron | <<locked>> | 88% | 54,926 psi | 86% | 3156 fps | 97% |
| IMR 4198 | <<locked>> | 82% | 57,638 psi | 90% | 3110 fps | 100% |
| IMR 4350ᴾ | <<locked>> | 100% | 56,652 psi | 89% | 3228 fps | 96.9% |
| IMR 4451 Enduron | <<locked>> | 94% | 54,940 psi | 86% | 3182 fps | 96.9% |
| IMR 4831ᴾ | <<locked>> | 100% | 54,636 psi | 86% | 3238 fps | 99.3% |
| IMR 4895 | <<locked>> | 90% | 57,537 psi | 90% | 3284 fps | 99.9% |
| IMR 8208 XBR | <<locked>> | 86% | 56,695 psi | 89% | 3209 fps | 100% |
| Lovex D073.5 | <<locked>> | 82% | 56,826 psi | 89% | 3186 fps | 100% |
| Lovex D073.6 | <<locked>> | 88% | 57,696 psi | 90% | 3232 fps | 100% |
| Lovex S060 | <<locked>> | 88% | 57,174 psi | 90% | 3179 fps | 99.9% |
| Lovex S062 | <<locked>> | 90% | 54,520 psi | 85% | 3179 fps | 100% |
| Lovex S065 | <<locked>> | 98% | 57,522 psi | 90% | 3232 fps | 98.6% |
| Lovex S070 | <<locked>> | 98% | 54,839 psi | 86% | 3205 fps | 97.3% |
| Norma 201 | <<locked>> | 88% | 56,405 psi | 88% | 3199 fps | 100% |
| Norma 202 | <<locked>> | 88% | 57,000 psi | 89% | 3202 fps | 100% |
| Norma 203B | <<locked>> | 90% | 55,259 psi | 87% | 3235 fps | 99.8% |
| Norma URPᴾ | <<locked>> | 100% | 56,898 psi | 89% | 3297 fps | 99.4% |
| Ramshot Big Game | <<locked>> | 90% | 56,130 psi | 88% | 3261 fps | 99.8% |
| Ramshot Hunterᴾ | <<locked>> | 100% | 55,753 psi | 87% | 3287 fps | 98.1% |
| Ramshot TAC | <<locked>> | 86% | 57,464 psi | 90% | 3225 fps | 98.7% |
| Ramshot Wild Boar | <<locked>> | 86% | 56,811 psi | 89% | 3241 fps | 99.9% |
| Ramshot X-Terminator | <<locked>> | 82% | 54,085 psi | 85% | 3146 fps | 99.6% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,592 psi | 56% | 2051 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 82% | 56,159 psi | 88% | 3186 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 92% | 57,580 psi | 90% | 3232 fps | 98.1% |
| ReloadSwiss RS 52 | <<locked>> | 88% | 56,623 psi | 89% | 3323 fps | 99.7% |
| ReloadSwiss RS 60 | <<locked>> | 94% | 56,536 psi | 89% | 3360 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 53,853 psi | 84% | 3268 fps | 98.9% |
| ReloadSwiss RS 70ᴾ | <<locked>> | 100% | 57,711 psi | 90% | 3369 fps | 99.3% |
| Rottweil R 901 | <<locked>> | 86% | 56,869 psi | 89% | 3179 fps | 100% |
| Rottweil R 902 | <<locked>> | 90% | 56,724 psi | 89% | 3196 fps | 100% |
| Rottweil R 903 | <<locked>> | 94% | 55,869 psi | 88% | 3228 fps | 100% |
| Rottweil R 907 | <<locked>> | 96% | 56,086 psi | 88% | 3199 fps | 96.7% |
| Shooters World Long Rifle | <<locked>> | 98% | 57,522 psi | 90% | 3232 fps | 98.6% |
| Shooters World Match Rifle | <<locked>> | 88% | 57,696 psi | 90% | 3232 fps | 100% |
| Shooters World Precision | <<locked>> | 90% | 54,520 psi | 85% | 3179 fps | 100% |
| Shooters World SW4350 | <<locked>> | 98% | 54,839 psi | 86% | 3205 fps | 97.3% |
| SNPE Vectan SP 11 | <<locked>> | 92% | 54,157 psi | 85% | 3235 fps | 99.7% |
| SNPE Vectan SP 7 | <<locked>> | 86% | 55,535 psi | 87% | 3192 fps | 98.8% |
| SNPE Vectan SP 9 | <<locked>> | 88% | 56,304 psi | 88% | 3225 fps | 99.8% |
| SNPE Vectan Tubal 3000 | <<locked>> | 86% | 54,360 psi | 85% | 3084 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 92% | 54,752 psi | 86% | 3077 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 96% | 54,491 psi | 85% | 3120 fps | 96.9% |
| Somchem S321 | <<locked>> | 82% | 54,549 psi | 85% | 3182 fps | 100% |
| Somchem S335 | <<locked>> | 88% | 57,334 psi | 90% | 3130 fps | 100% |
| Somchem S341 | <<locked>> | 86% | 55,405 psi | 87% | 3189 fps | 99.8% |
| Somchem S355 | <<locked>> | 94% | 56,260 psi | 88% | 3228 fps | 99.9% |
| Somchem S365ᴾ | <<locked>> | 100% | 50,937 psi | 80% | 3235 fps | 100% |
| Vihtavuori N130 | <<locked>> | 84% | 57,667 psi | 90% | 3097 fps | 100% |
| Vihtavuori N133 | <<locked>> | 86% | 54,636 psi | 86% | 3068 fps | 100% |
| Vihtavuori N135 | <<locked>> | 90% | 56,739 psi | 89% | 3159 fps | 100% |
| Vihtavuori N140 | <<locked>> | 88% | 54,259 psi | 85% | 3127 fps | 100% |
| Vihtavuori N150 | <<locked>> | 94% | 54,215 psi | 85% | 3150 fps | 100% |
| Vihtavuori N160 | <<locked>> | 98% | 55,724 psi | 87% | 3235 fps | 99.2% |
| Vihtavuori N530 | <<locked>> | 86% | 57,377 psi | 90% | 3209 fps | 100% |
| Vihtavuori N540 | <<locked>> | 90% | 55,970 psi | 88% | 3169 fps | 100% |
| Vihtavuori N550 | <<locked>> | 98% | 54,752 psi | 86% | 3235 fps | 99% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 43,120 psi | 68% | 3084 fps | 97.9% |
| Winchester 6.5 StaBALL | <<locked>> | 98% | 56,260 psi | 88% | 3209 fps | 100% |
| Winchester 748 | <<locked>> | 86% | 57,595 psi | 90% | 3261 fps | 100% |
| Winchester 760 | <<locked>> | 98% | 57,087 psi | 89% | 3304 fps | 97.6% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 35,157 psi | 55% | 2979 fps | 97.4% |
| Winchester StaBALL Match | <<locked>> | 88% | 56,391 psi | 88% | 3235 fps | 100% |
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 2015 | <<locked>> | 80% | 48,414 psi | 76% | 2995 fps | 100% |
| Accurate 2460 | <<locked>> | 80% | 53,171 psi | 83% | 3120 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 40,712 psi | 64% | 2897 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 48,341 psi | 76% | 3071 fps | 100% |
| Accurate 2700 | <<locked>> | 88% | 53,084 psi | 83% | 3104 fps | 95.8% |
| Accurate 4064 | <<locked>> | 80% | 38,537 psi | 60% | 2884 fps | 99.8% |
| Accurate 4350 | <<locked>> | 88% | 37,652 psi | 59% | 2917 fps | 95.5% |
| ADI AR 2206H | <<locked>> | 80% | 44,527 psi | 70% | 3015 fps | 98.5% |
| ADI AR 2208 | <<locked>> | 80% | 37,811 psi | 59% | 2841 fps | 96.1% |
| ADI Benchmark 8208 | <<locked>> | 80% | 46,644 psi | 73% | 3028 fps | 99.6% |
| Alliant AR-Comp | <<locked>> | 80% | 47,094 psi | 74% | 3025 fps | 100% |
| Alliant Power Pro 2000-MR | 43.7 gr | 80% | 40,683 psi | 64% | 3038 fps | 96.8% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 37,507 psi | 59% | 2867 fps | 97.7% |
| Alliant Reloder-15 | <<locked>> | 80% | 40,176 psi | 63% | 2933 fps | 97% |
| Alliant Reloder-16 | <<locked>> | 88% | 37,652 psi | 59% | 2933 fps | 95.6% |
| Alliant Reloder-17 | <<locked>> | 80% | 32,474 psi | 51% | 2815 fps | 95.2% |
| Alliant Reloder-23 | <<locked>> | 94% | 32,416 psi | 51% | 2808 fps | 95.1% |
| Alliant Reloder-26 | <<locked>> | 98% | 41,278 psi | 65% | 3100 fps | 96.2% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 44,179 psi | 69% | 3018 fps | 97.5% |
| Bofors RP3 | <<locked>> | 80% | 37,057 psi | 58% | 2867 fps | 97.7% |
| Bofors RP7 | <<locked>> | 92% | 49,327 psi | 77% | 3077 fps | 95.1% |
| Hodgdon Benchmark | <<locked>> | 80% | 48,428 psi | 76% | 3022 fps | 99.9% |
| Hodgdon BL-C2 | <<locked>> | 80% | 45,658 psi | 72% | 3048 fps | 99.7% |
| Hodgdon CFE223 | <<locked>> | 80% | 50,647 psi | 79% | 3212 fps | 99.1% |
| Hodgdon H322 | <<locked>> | 80% | 53,664 psi | 84% | 3146 fps | 100% |
| Hodgdon H380 | <<locked>> | 82% | 40,698 psi | 64% | 2933 fps | 95.8% |
| Hodgdon H414 | <<locked>> | 92% | 46,383 psi | 73% | 3107 fps | 95.1% |
| Hodgdon H4350 | <<locked>> | 94% | 54,114 psi | 85% | 3205 fps | 95.5% |
| Hodgdon H4895 | <<locked>> | 80% | 44,933 psi | 70% | 3028 fps | 99% |
| Hodgdon Hybrid 100V | <<locked>> | 86% | 32,285 psi | 51% | 2753 fps | 95.4% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 41,278 psi | 65% | 2992 fps | 98.7% |
| Hodgdon Superformance | 53.5 gr | 94% | 50,357 psi | 79% | 3205 fps | 95.6% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,063 psi | 41% | 1795 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 43,294 psi | 68% | 2976 fps | 98.7% |
| IMR 3031 | <<locked>> | 80% | 44,860 psi | 70% | 3035 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 39,668 psi | 62% | 2884 fps | 97% |
| IMR 4166 Enduron | <<locked>> | 84% | 48,196 psi | 76% | 3031 fps | 95.5% |
| IMR 4198 | <<locked>> | 80% | 54,389 psi | 85% | 3064 fps | 100% |
| IMR 4350 | <<locked>> | 96% | 49,951 psi | 78% | 3110 fps | 95.4% |
| IMR 4451 Enduron | <<locked>> | 90% | 48,196 psi | 76% | 3058 fps | 95.4% |
| IMR 4831 | <<locked>> | 88% | 36,390 psi | 57% | 2867 fps | 95.1% |
| IMR 4895 | <<locked>> | 80% | 41,176 psi | 65% | 2969 fps | 97.9% |
| IMR 8208 XBR | <<locked>> | 80% | 46,644 psi | 73% | 3028 fps | 99.6% |
| Lovex D073.5 | <<locked>> | 80% | 52,939 psi | 83% | 3127 fps | 100% |
| Lovex D073.6 | <<locked>> | 80% | 43,787 psi | 69% | 2992 fps | 99.9% |
| Lovex S060 | <<locked>> | 80% | 44,585 psi | 70% | 2953 fps | 98.6% |
| Lovex S062 | <<locked>> | 80% | 39,508 psi | 62% | 2887 fps | 98.6% |
| Lovex S065 | <<locked>> | 88% | 42,003 psi | 66% | 2933 fps | 95.3% |
| Lovex S070 | <<locked>> | 92% | 45,324 psi | 71% | 3025 fps | 95% |
| Norma 201 | <<locked>> | 80% | 43,656 psi | 68% | 2969 fps | 99.2% |
| Norma 202 | <<locked>> | 80% | 44,077 psi | 69% | 2979 fps | 100% |
| Norma 203B | <<locked>> | 80% | 39,566 psi | 62% | 2923 fps | 97.4% |
| Norma URP | <<locked>> | 88% | 37,942 psi | 59% | 2920 fps | 95.4% |
| Ramshot Big Game | <<locked>> | 80% | 39,363 psi | 62% | 2933 fps | 97.2% |
| Ramshot Hunter | <<locked>> | 94% | 45,382 psi | 71% | 3091 fps | 95.8% |
| Ramshot TAC | <<locked>> | 80% | 46,949 psi | 74% | 3035 fps | 96.9% |
| Ramshot Wild Boar | <<locked>> | 80% | 46,514 psi | 73% | 3058 fps | 98.8% |
| Ramshot X-Terminator | <<locked>> | 80% | 50,589 psi | 79% | 3084 fps | 99.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,440 psi | 41% | 1837 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 80% | 52,373 psi | 82% | 3123 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 84% | 43,976 psi | 69% | 2979 fps | 95% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 42,641 psi | 67% | 3054 fps | 97.6% |
| ReloadSwiss RS 60 | 43.1 gr | 80% | 34,621 psi | 54% | 2897 fps | 98.6% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 37,463 psi | 59% | 2933 fps | 95% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 40,379 psi | 63% | 3012 fps | 95.2% |
| Rottweil R 901 | <<locked>> | 80% | 47,326 psi | 74% | 3018 fps | 100% |
| Rottweil R 902 | <<locked>> | 80% | 41,452 psi | 65% | 2913 fps | 98.9% |
| Rottweil R 903 | <<locked>> | 80% | 34,737 psi | 54% | 2802 fps | 96.7% |
| Rottweil R 907 | <<locked>> | 92% | 49,327 psi | 77% | 3077 fps | 95.1% |
| Shooters World Long Rifle | <<locked>> | 88% | 42,003 psi | 66% | 2933 fps | 95.3% |
| Shooters World Match Rifle | <<locked>> | 80% | 43,787 psi | 69% | 2992 fps | 99.9% |
| Shooters World Precision | <<locked>> | 80% | 39,508 psi | 62% | 2887 fps | 98.6% |
| Shooters World SW4350 | <<locked>> | 92% | 45,324 psi | 71% | 3025 fps | 95% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 36,013 psi | 56% | 2858 fps | 96.2% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 44,933 psi | 70% | 2999 fps | 96.9% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 43,294 psi | 68% | 2982 fps | 98.3% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 44,918 psi | 70% | 2923 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 37,333 psi | 59% | 2766 fps | 99.9% |
| SNPE Vectan Tubal 7000 | <<locked>> | 92% | 47,514 psi | 74% | 2995 fps | 95.4% |
| Somchem S321 | <<locked>> | 80% | 50,908 psi | 80% | 3120 fps | 99.9% |
| Somchem S335 | <<locked>> | 80% | 44,701 psi | 70% | 2923 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 44,947 psi | 70% | 3002 fps | 98.5% |
| Somchem S355 | <<locked>> | 80% | 35,752 psi | 56% | 2815 fps | 96.8% |
| Somchem S365 | <<locked>> | 84% | 29,486 psi | 46% | 2730 fps | 95.6% |
| Vihtavuori N130 | <<locked>> | 80% | 50,778 psi | 80% | 2995 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 45,310 psi | 71% | 2917 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 40,857 psi | 64% | 2897 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 41,669 psi | 65% | 2904 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 33,939 psi | 53% | 2743 fps | 97.6% |
| Vihtavuori N160 | <<locked>> | 86% | 36,941 psi | 58% | 2861 fps | 95% |
| Vihtavuori N530 | <<locked>> | 80% | 46,905 psi | 74% | 3028 fps | 99.6% |
| Vihtavuori N540 | <<locked>> | 80% | 40,059 psi | 63% | 2884 fps | 99.8% |
| Vihtavuori N550 | <<locked>> | 88% | 38,943 psi | 61% | 2920 fps | 95.5% |
| Vihtavuori N555 | <<locked>> | 94% | 35,041 psi | 55% | 2894 fps | 95.3% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 32,387 psi | 51% | 2710 fps | 95.6% |
| Winchester 748 | <<locked>> | 80% | 46,833 psi | 73% | 3077 fps | 99.9% |
| Winchester 760 | <<locked>> | 92% | 46,673 psi | 73% | 3114 fps | 95.2% |
| Winchester StaBALL HD | <<locked>> | 98% | 32,793 psi | 51% | 2897 fps | 96% |
| Winchester StaBALL Match | <<locked>> | 80% | 42,844 psi | 67% | 2986 fps | 98.7% |
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 113 powders for .255 GS loaded with the .257 | 95gr | Hammer HHT. ReloadSwiss RS 70 delivers the highest muzzle velocity at 3,369 fps; across all powders the maximum-charge window runs from 2,008 fps to 3,369 fps. Accurate 3100 gives the best case fill at 100 %, and 113 of the 113 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 53–90 %, leaving at least 10 % headroom. The 95.0 gr projectile in 0.257" calls for a 1:9.5 twist; slower twists will usually not stabilise this weight. Accurate 3100, ADI AR 2209, Alliant Reloder-16 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 Power Pro 2000-MR, ReloadSwiss RS 60, Hodgdon Superformance rank at the top here: for .255 GS with the .257 | 95gr | Hammer HHT they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Accurate 3100, ADI AR 2209, Alliant Reloder-19 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.