Load Specifications
Load data in caliber .255 GS with .257 | 88gr | Osprey Virtus bullet and 97 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 60, Alliant Reloder-17 and Alliant Power Pro 2000-MR.
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.
A valid access license is required to use the Personalized Load Calculator.
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>> | 86% | 56,811 psi | 89% | 3245 fps | 100% |
| Accurate 2460 | <<locked>> | 82% | 55,187 psi | 86% | 3264 fps | 100% |
| Accurate 2495 | <<locked>> | 90% | 55,361 psi | 87% | 3258 fps | 100% |
| Accurate 2520 | <<locked>> | 86% | 57,653 psi | 90% | 3337 fps | 100% |
| Accurate 4064 | <<locked>> | 92% | 55,332 psi | 87% | 3307 fps | 100% |
| Accurate 4350ᴾ | <<locked>> | 100% | 56,072 psi | 88% | 3389 fps | 99% |
| ADI AR 2206H | <<locked>> | 88% | 56,159 psi | 88% | 3346 fps | 99.6% |
| ADI AR 2208 | <<locked>> | 94% | 57,348 psi | 90% | 3340 fps | 99.4% |
| ADI Benchmark 8208 | <<locked>> | 86% | 55,347 psi | 87% | 3297 fps | 99.9% |
| Alliant AR-Comp | <<locked>> | 86% | 55,927 psi | 88% | 3278 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 82% | 57,101 psi | 89% | 3422 fps | 99.9% |
| Alliant Power Pro 2000-MR | <<locked>> | 90% | 56,507 psi | 89% | 3478 fps | 99.4% |
| Alliant Reloder- TS 15.5 | <<locked>> | 94% | 57,435 psi | 90% | 3366 fps | 100% |
| Alliant Reloder-10x | <<locked>> | 82% | 56,173 psi | 88% | 3251 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 90% | 54,433 psi | 85% | 3330 fps | 99.2% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 53,664 psi | 84% | 3392 fps | 99% |
| Alliant Reloder-17 | <<locked>> | 96% | 54,955 psi | 86% | 3438 fps | 99.9% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 37,971 psi | 60% | 3054 fps | 96.7% |
| Baschieri & Pellagri 107 | <<locked>> | 88% | 56,652 psi | 89% | 3360 fps | 99.1% |
| Bofors RP3 | <<locked>> | 92% | 54,462 psi | 85% | 3323 fps | 99.9% |
| Hodgdon Benchmark | <<locked>> | 86% | 57,058 psi | 89% | 3281 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 86% | 54,621 psi | 86% | 3320 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 84% | 56,855 psi | 89% | 3432 fps | 99.4% |
| Hodgdon H322 | <<locked>> | 82% | 55,709 psi | 87% | 3294 fps | 100% |
| Hodgdon H335 | <<locked>> | 82% | 57,043 psi | 89% | 3320 fps | 100% |
| Hodgdon H380 | <<locked>> | 92% | 55,535 psi | 87% | 3333 fps | 98.5% |
| Hodgdon H414 | <<locked>> | 98% | 55,477 psi | 87% | 3383 fps | 96.7% |
| Hodgdon H4895 | <<locked>> | 88% | 56,739 psi | 89% | 3360 fps | 99.8% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 49,588 psi | 78% | 3248 fps | 99.3% |
| Hodgdon LEVERevolution | <<locked>> | 90% | 56,608 psi | 89% | 3392 fps | 100% |
| Hodgdon Superformance | <<locked>> | 98% | 56,565 psi | 89% | 3419 fps | 96.4% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 34,925 psi | 55% | 2087 fps | 100% |
| Hodgdon VARGET | <<locked>> | 88% | 54,766 psi | 86% | 3304 fps | 99.7% |
| IMR 3031 | <<locked>> | 88% | 56,768 psi | 89% | 3350 fps | 100% |
| IMR 4064 | <<locked>> | 92% | 56,811 psi | 89% | 3323 fps | 99.5% |
| IMR 4166 Enduron | <<locked>> | 90% | 57,217 psi | 90% | 3304 fps | 96.8% |
| IMR 4198 | <<locked>> | 82% | 56,260 psi | 88% | 3212 fps | 100% |
| IMR 4350ᴾ | <<locked>> | 100% | 55,259 psi | 87% | 3307 fps | 95.9% |
| IMR 4451 Enduron | <<locked>> | 96% | 57,014 psi | 89% | 3323 fps | 96.7% |
| IMR 4831ᴾ | <<locked>> | 100% | 52,721 psi | 83% | 3314 fps | 98.6% |
| IMR 4895 | <<locked>> | 90% | 55,840 psi | 88% | 3369 fps | 99.6% |
| IMR 8208 XBR | <<locked>> | 86% | 55,347 psi | 87% | 3297 fps | 99.9% |
| Lovex D073.5 | <<locked>> | 82% | 55,216 psi | 87% | 3274 fps | 100% |
| Lovex D073.6 | <<locked>> | 88% | 56,231 psi | 88% | 3320 fps | 100% |
| Lovex S060 | <<locked>> | 88% | 55,912 psi | 88% | 3271 fps | 99.6% |
| Lovex S062 | <<locked>> | 92% | 56,391 psi | 88% | 3320 fps | 100% |
| Lovex S065 | <<locked>> | 98% | 55,956 psi | 88% | 3310 fps | 97.9% |
| Lovex S070ᴾ | <<locked>> | 100% | 56,985 psi | 89% | 3343 fps | 97.1% |
| Norma 201 | <<locked>> | 88% | 54,665 psi | 86% | 3284 fps | 99.9% |
| Norma 202 | <<locked>> | 88% | 55,506 psi | 87% | 3294 fps | 100% |
| Norma 203B | <<locked>> | 92% | 57,058 psi | 89% | 3376 fps | 99.7% |
| Norma URPᴾ | <<locked>> | 100% | 54,984 psi | 86% | 3373 fps | 98.8% |
| Ramshot Big Game | <<locked>> | 90% | 54,447 psi | 85% | 3343 fps | 99.4% |
| Ramshot Hunterᴾ | <<locked>> | 100% | 54,041 psi | 85% | 3363 fps | 97.3% |
| Ramshot TAC | <<locked>> | 86% | 55,782 psi | 87% | 3304 fps | 98% |
| Ramshot Wild Boar | <<locked>> | 86% | 55,463 psi | 87% | 3330 fps | 99.5% |
| Ramshot X-Terminator | <<locked>> | 84% | 56,347 psi | 88% | 3294 fps | 99.6% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,447 psi | 56% | 2136 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 82% | 54,578 psi | 86% | 3278 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 92% | 56,028 psi | 88% | 3314 fps | 97.3% |
| ReloadSwiss RS 52 | <<locked>> | 88% | 55,042 psi | 86% | 3409 fps | 99.2% |
| ReloadSwiss RS 60 | <<locked>> | 94% | 54,650 psi | 86% | 3442 fps | 100% |
| ReloadSwiss RS 62ᴾ | <<locked>> | 100% | 55,927 psi | 88% | 3409 fps | 98.8% |
| ReloadSwiss RS 70ᴾ | <<locked>> | 100% | 55,854 psi | 88% | 3442 fps | 98.6% |
| Rottweil R 901 | <<locked>> | 86% | 55,347 psi | 87% | 3271 fps | 100% |
| Rottweil R 902 | <<locked>> | 90% | 55,288 psi | 87% | 3284 fps | 99.9% |
| Rottweil R 903 | <<locked>> | 94% | 54,317 psi | 85% | 3314 fps | 99.8% |
| Shooters World Long Rifle | <<locked>> | 98% | 55,956 psi | 88% | 3310 fps | 97.9% |
| Shooters World Match Rifle | <<locked>> | 88% | 56,231 psi | 88% | 3320 fps | 100% |
| Shooters World Precision | <<locked>> | 92% | 56,391 psi | 88% | 3320 fps | 100% |
| Shooters World SW4350ᴾ | <<locked>> | 100% | 56,985 psi | 89% | 3343 fps | 97.1% |
| SNPE Vectan SP 11 | <<locked>> | 94% | 56,362 psi | 88% | 3383 fps | 99.6% |
| SNPE Vectan SP 3 | <<locked>> | 88% | 56,681 psi | 89% | 3212 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 86% | 54,157 psi | 85% | 3278 fps | 98.2% |
| SNPE Vectan SP 9 | <<locked>> | 88% | 55,013 psi | 86% | 3310 fps | 99.5% |
| SNPE Vectan Tubal 3000 | <<locked>> | 88% | 56,434 psi | 88% | 3228 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 94% | 56,855 psi | 89% | 3222 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 98% | 56,521 psi | 89% | 3255 fps | 96.7% |
| Somchem S321 | <<locked>> | 84% | 56,768 psi | 89% | 3330 fps | 100% |
| Somchem S335 | <<locked>> | 88% | 55,680 psi | 87% | 3222 fps | 100% |
| Somchem S341 | <<locked>> | 86% | 53,693 psi | 84% | 3271 fps | 99.4% |
| Somchem S355 | <<locked>> | 94% | 54,491 psi | 85% | 3310 fps | 99.7% |
| Somchem S365ᴾ | <<locked>> | 100% | 49,298 psi | 77% | 3314 fps | 99.9% |
| Vihtavuori N130 | <<locked>> | 84% | 55,999 psi | 88% | 3192 fps | 100% |
| Vihtavuori N133 | <<locked>> | 88% | 56,681 psi | 89% | 3212 fps | 100% |
| Vihtavuori N135 | <<locked>> | 90% | 54,897 psi | 86% | 3251 fps | 100% |
| Vihtavuori N140 | <<locked>> | 90% | 56,217 psi | 88% | 3268 fps | 100% |
| Vihtavuori N150 | <<locked>> | 96% | 56,289 psi | 88% | 3291 fps | 100% |
| Vihtavuori N160 | <<locked>> | 98% | 53,925 psi | 85% | 3310 fps | 98.6% |
| Vihtavuori N530 | <<locked>> | 86% | 55,956 psi | 88% | 3297 fps | 100% |
| Vihtavuori N540 | <<locked>> | 90% | 54,346 psi | 85% | 3258 fps | 100% |
| Vihtavuori N550ᴾ | <<locked>> | 100% | 56,710 psi | 89% | 3373 fps | 98.8% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 41,365 psi | 65% | 3146 fps | 96.7% |
| Winchester 6.5 StaBALL | <<locked>> | 98% | 54,621 psi | 86% | 3287 fps | 99.9% |
| Winchester 748 | <<locked>> | 86% | 55,883 psi | 88% | 3346 fps | 100% |
| Winchester 760 | <<locked>> | 98% | 55,477 psi | 87% | 3383 fps | 96.7% |
| Winchester StaBALL Match | <<locked>> | 88% | 54,955 psi | 86% | 3320 fps | 99.8% |
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% | 46,920 psi | 74% | 3084 fps | 100% |
| Accurate 2460 | <<locked>> | 80% | 51,547 psi | 81% | 3202 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 39,175 psi | 61% | 2969 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 46,717 psi | 73% | 3150 fps | 99.9% |
| Accurate 4064 | <<locked>> | 80% | 37,072 psi | 58% | 2949 fps | 99.4% |
| Accurate 4350 | <<locked>> | 90% | 38,856 psi | 61% | 3041 fps | 95.1% |
| ADI AR 2206H | <<locked>> | 80% | 43,279 psi | 68% | 3091 fps | 97.7% |
| ADI AR 2208 | <<locked>> | 80% | 36,840 psi | 58% | 2913 fps | 95% |
| ADI Benchmark 8208 | <<locked>> | 80% | 45,440 psi | 71% | 3110 fps | 99.1% |
| Alliant AR-Comp | <<locked>> | 80% | 45,687 psi | 72% | 3117 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 80% | 53,185 psi | 83% | 3353 fps | 99.6% |
| Alliant Power Pro 2000-MR | 44.9 gr | 80% | 39,537 psi | 62% | 3104 fps | 95.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 36,172 psi | 57% | 2933 fps | 96.6% |
| Alliant Reloder-10x | <<locked>> | 80% | 52,707 psi | 83% | 3199 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 39,001 psi | 61% | 3005 fps | 96% |
| Alliant Reloder-16 | <<locked>> | 90% | 38,957 psi | 61% | 3064 fps | 95.2% |
| Alliant Reloder-17 | 46.4 gr | 84% | 36,056 psi | 56% | 3012 fps | 96% |
| Alliant Reloder-23 | <<locked>> | 98% | 35,665 psi | 56% | 2989 fps | 95.8% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 42,699 psi | 67% | 3087 fps | 96.5% |
| Bofors RP3 | <<locked>> | 80% | 35,766 psi | 56% | 2930 fps | 96.6% |
| Hodgdon Benchmark | <<locked>> | 80% | 47,297 psi | 74% | 3110 fps | 99.6% |
| Hodgdon BL-C2 | <<locked>> | 80% | 44,425 psi | 70% | 3127 fps | 99.3% |
| Hodgdon CFE223 | <<locked>> | 80% | 49,095 psi | 77% | 3291 fps | 98.4% |
| Hodgdon H322 | <<locked>> | 80% | 52,257 psi | 82% | 3241 fps | 100% |
| Hodgdon H335 | <<locked>> | 80% | 53,287 psi | 84% | 3261 fps | 100% |
| Hodgdon H380 | <<locked>> | 84% | 42,250 psi | 66% | 3071 fps | 95.6% |
| Hodgdon H414 | <<locked>> | 96% | 51,721 psi | 81% | 3314 fps | 95.8% |
| Hodgdon H4895 | <<locked>> | 80% | 43,700 psi | 68% | 3107 fps | 98.3% |
| Hodgdon Hybrid 100V | <<locked>> | 90% | 35,491 psi | 56% | 2933 fps | 95.9% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 39,813 psi | 62% | 3061 fps | 97.8% |
| Hodgdon Superformance | <<locked>> | 96% | 52,388 psi | 82% | 3343 fps | 95.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 25,976 psi | 41% | 1870 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 42,105 psi | 66% | 3054 fps | 97.9% |
| IMR 3031 | <<locked>> | 80% | 43,236 psi | 68% | 3114 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 38,653 psi | 61% | 2956 fps | 96% |
| IMR 4166 Enduron | <<locked>> | 86% | 50,096 psi | 79% | 3169 fps | 95.2% |
| IMR 4198 | <<locked>> | 80% | 53,127 psi | 83% | 3163 fps | 100% |
| IMR 4350 | <<locked>> | 98% | 51,619 psi | 81% | 3238 fps | 95% |
| IMR 4451 Enduron | <<locked>> | 92% | 50,212 psi | 79% | 3199 fps | 95.2% |
| IMR 4831 | <<locked>> | 92% | 40,089 psi | 63% | 3051 fps | 95.6% |
| IMR 4895 | <<locked>> | 80% | 39,972 psi | 63% | 3045 fps | 96.9% |
| IMR 8208 XBR | <<locked>> | 80% | 45,440 psi | 71% | 3110 fps | 99.1% |
| Lovex D073.5 | <<locked>> | 80% | 51,561 psi | 81% | 3212 fps | 100% |
| Lovex D073.6 | <<locked>> | 80% | 42,308 psi | 66% | 3068 fps | 99.6% |
| Lovex S060 | <<locked>> | 80% | 43,569 psi | 68% | 3031 fps | 97.8% |
| Lovex S062 | <<locked>> | 80% | 38,421 psi | 60% | 2959 fps | 97.8% |
| Lovex S065 | <<locked>> | 90% | 43,468 psi | 68% | 3064 fps | 95% |
| Lovex S070 | <<locked>> | 96% | 50,053 psi | 78% | 3219 fps | 95.6% |
| Norma 201 | <<locked>> | 80% | 42,279 psi | 66% | 3041 fps | 98.6% |
| Norma 202 | <<locked>> | 80% | 42,598 psi | 67% | 3058 fps | 99.8% |
| Norma 203B | <<locked>> | 80% | 38,348 psi | 60% | 2992 fps | 96.4% |
| Norma URP | <<locked>> | 90% | 39,175 psi | 61% | 3048 fps | 95% |
| Ramshot Big Game | <<locked>> | 80% | 38,189 psi | 60% | 3002 fps | 96.1% |
| Ramshot Hunter | <<locked>> | 96% | 47,065 psi | 74% | 3225 fps | 95.6% |
| Ramshot TAC | <<locked>> | 80% | 45,513 psi | 71% | 3104 fps | 95.8% |
| Ramshot Wild Boar | <<locked>> | 80% | 45,020 psi | 71% | 3130 fps | 98.1% |
| Ramshot X-Terminator | <<locked>> | 80% | 49,443 psi | 77% | 3169 fps | 98.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,295 psi | 41% | 1916 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 80% | 51,314 psi | 80% | 3219 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 88% | 48,965 psi | 77% | 3179 fps | 95.7% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 41,089 psi | 64% | 3123 fps | 96.5% |
| ReloadSwiss RS 60 | 44.2 gr | 80% | 33,460 psi | 52% | 2953 fps | 97.5% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 41,843 psi | 66% | 3133 fps | 95.7% |
| ReloadSwiss RS 70 | <<locked>> | 94% | 44,962 psi | 70% | 3215 fps | 95.9% |
| Rottweil R 901 | <<locked>> | 80% | 45,948 psi | 72% | 3100 fps | 99.9% |
| Rottweil R 902 | <<locked>> | 80% | 40,147 psi | 63% | 2986 fps | 98.1% |
| Rottweil R 903 | <<locked>> | 80% | 33,591 psi | 53% | 2864 fps | 95.4% |
| Shooters World Long Rifle | <<locked>> | 90% | 43,468 psi | 68% | 3064 fps | 95% |
| Shooters World Match Rifle | <<locked>> | 80% | 42,308 psi | 66% | 3068 fps | 99.6% |
| Shooters World Precision | <<locked>> | 80% | 38,421 psi | 60% | 2959 fps | 97.8% |
| Shooters World SW4350 | <<locked>> | 96% | 50,053 psi | 78% | 3219 fps | 95.6% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 37,333 psi | 59% | 2989 fps | 95.9% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 44,034 psi | 69% | 3005 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 43,714 psi | 69% | 3071 fps | 95.9% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 41,974 psi | 66% | 3054 fps | 97.4% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 43,685 psi | 68% | 3005 fps | 99.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 36,187 psi | 57% | 2841 fps | 99.6% |
| SNPE Vectan Tubal 7000 | <<locked>> | 94% | 49,400 psi | 77% | 3130 fps | 95.1% |
| Somchem S321 | <<locked>> | 80% | 49,298 psi | 77% | 3202 fps | 99.7% |
| Somchem S335 | <<locked>> | 80% | 43,337 psi | 68% | 3002 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 43,439 psi | 68% | 3071 fps | 97.7% |
| Somchem S355 | <<locked>> | 80% | 34,461 psi | 54% | 2877 fps | 95.5% |
| Somchem S365 | <<locked>> | 86% | 30,313 psi | 48% | 2841 fps | 95.1% |
| Vihtavuori N130 | <<locked>> | 80% | 49,429 psi | 77% | 3087 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 44,034 psi | 69% | 3005 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 39,494 psi | 62% | 2976 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 40,495 psi | 63% | 2986 fps | 99.8% |
| Vihtavuori N150 | <<locked>> | 80% | 32,895 psi | 52% | 2808 fps | 96.6% |
| Vihtavuori N160 | <<locked>> | 90% | 41,046 psi | 64% | 3054 fps | 95.6% |
| Vihtavuori N530 | <<locked>> | 80% | 45,614 psi | 71% | 3110 fps | 99.2% |
| Vihtavuori N540 | <<locked>> | 80% | 38,856 psi | 61% | 2959 fps | 99.4% |
| Vihtavuori N550 | <<locked>> | 90% | 40,321 psi | 63% | 3048 fps | 95.2% |
| Vihtavuori N555 | <<locked>> | 98% | 38,653 psi | 61% | 3081 fps | 95.9% |
| Winchester 6.5 StaBALL | <<locked>> | 84% | 33,634 psi | 53% | 2835 fps | 95.3% |
| Winchester 748 | <<locked>> | 80% | 45,295 psi | 71% | 3153 fps | 99.6% |
| Winchester 760 | <<locked>> | 96% | 51,721 psi | 81% | 3314 fps | 95.8% |
| Winchester StaBALL Match | <<locked>> | 80% | 41,423 psi | 65% | 3054 fps | 97.8% |
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 97 powders for .255 GS loaded with the .257 | 88gr | Osprey Virtus. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,478 fps; across all powders the maximum-charge window runs from 2,087 fps to 3,478 fps. Accurate 4350 gives the best case fill at 100 %, and 97 of the 97 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 55–90 %, leaving at least 10 % headroom. The 88.0 gr projectile in 0.257" calls for a 1:10.5 twist; slower twists will usually not stabilise this weight. Accurate 4350, Alliant Reloder-16, 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. ReloadSwiss RS 60, Alliant Reloder-17, Alliant Power Pro 2000-MR rank at the top here: for .255 GS with the .257 | 88gr | Osprey Virtus 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.