Load Specifications
Load data in caliber .255 GS with .257 | 117gr | Sellier & Bellot SPFN bullet and 96 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 70, Alliant Reloder-26 and Alliant Reloder-17.
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 2495 | <<locked>> | 82% | 55,579 psi | 87% | 2848 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 56,826 psi | 89% | 2920 fps | 98.8% |
| Accurate 3100ᴾ | <<locked>> | 100% | 54,955 psi | 86% | 2963 fps | 99.6% |
| Accurate 4064 | <<locked>> | 84% | 55,854 psi | 88% | 2904 fps | 100% |
| Accurate 4350 | <<locked>> | 92% | 56,942 psi | 89% | 3015 fps | 100% |
| Accurate MAGPROᴾ | <<locked>> | 100% | 56,971 psi | 89% | 3104 fps | 96.2% |
| ADI AR 2208 | <<locked>> | 86% | 55,796 psi | 87% | 2936 fps | 100% |
| ADI AR 2209 | <<locked>> | 96% | 53,998 psi | 85% | 2999 fps | 97.8% |
| ADI AR 2213ᴾ | <<locked>> | 100% | 55,332 psi | 87% | 3048 fps | 96.8% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 55,288 psi | 87% | 3061 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 86% | 56,666 psi | 89% | 2959 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 84% | 56,985 psi | 89% | 2982 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 94% | 57,334 psi | 90% | 3071 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 88% | 55,347 psi | 87% | 3045 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 98% | 57,145 psi | 90% | 3048 fps | 98.4% |
| Alliant Reloder-22ᴾ | <<locked>> | 100% | 54,302 psi | 85% | 3045 fps | 98.1% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 51,401 psi | 81% | 2979 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 44,773 psi | 70% | 2900 fps | 99.1% |
| Alliant Reloder-26 | <<locked>> | 98% | 55,216 psi | 87% | 3123 fps | 100% |
| Bofors RP15ᴾ | <<locked>> | 100% | 49,937 psi | 78% | 2969 fps | 97.1% |
| Bofors RP3 | <<locked>> | 84% | 54,143 psi | 85% | 2927 fps | 100% |
| Bofors RP5ᴾ | <<locked>> | 100% | 54,302 psi | 85% | 3045 fps | 98.1% |
| Bofors RP7 | <<locked>> | 90% | 56,913 psi | 89% | 2959 fps | 99% |
| Hodgdon H380 | <<locked>> | 84% | 54,491 psi | 85% | 2943 fps | 99.9% |
| Hodgdon H414 | <<locked>> | 90% | 55,405 psi | 87% | 3012 fps | 99.2% |
| Hodgdon H4350 | <<locked>> | 88% | 55,158 psi | 86% | 2972 fps | 98.3% |
| Hodgdon H4831 | <<locked>> | 98% | 55,608 psi | 87% | 2995 fps | 96.3% |
| Hodgdon H4831 SC | <<locked>> | 98% | 54,592 psi | 86% | 2979 fps | 96% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 54,186 psi | 85% | 2940 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 55,738 psi | 87% | 2979 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 43,671 psi | 68% | 2923 fps | 96.1% |
| Hodgdon Superformance | <<locked>> | 90% | 55,463 psi | 87% | 3045 fps | 99.1% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,492 psi | 57% | 1847 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 56,304 psi | 88% | 2940 fps | 100% |
| IMR 4064 | <<locked>> | 84% | 55,376 psi | 87% | 2920 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 82% | 54,534 psi | 85% | 2900 fps | 99% |
| IMR 4350 | <<locked>> | 92% | 54,476 psi | 85% | 2940 fps | 98.7% |
| IMR 4451 Enduron | <<locked>> | 88% | 55,201 psi | 87% | 2936 fps | 99.1% |
| IMR 4831 | <<locked>> | 94% | 57,130 psi | 90% | 3002 fps | 100% |
| IMR 4895 | <<locked>> | 82% | 55,056 psi | 86% | 2959 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 98% | 57,159 psi | 90% | 2982 fps | 96.8% |
| IMR 7828 SSCᴾ | <<locked>> | 100% | 52,881 psi | 83% | 3018 fps | 96.4% |
| Lovex S060 | <<locked>> | 82% | 56,971 psi | 89% | 2907 fps | 100% |
| Lovex S062 | <<locked>> | 84% | 55,651 psi | 87% | 2913 fps | 100% |
| Lovex S065 | <<locked>> | 90% | 55,376 psi | 87% | 2933 fps | 99.7% |
| Lovex S070 | <<locked>> | 92% | 56,797 psi | 89% | 2979 fps | 99.4% |
| Lovex S071ᴾ | <<locked>> | 100% | 45,571 psi | 71% | 2808 fps | 98.4% |
| Norma 201 | <<locked>> | 82% | 56,913 psi | 89% | 2923 fps | 100% |
| Norma 202 | <<locked>> | 82% | 57,522 psi | 90% | 2917 fps | 100% |
| Norma 203B | <<locked>> | 84% | 56,275 psi | 88% | 2969 fps | 100% |
| Norma 204 | <<locked>> | 92% | 55,303 psi | 87% | 2995 fps | 97.9% |
| Norma MRP | <<locked>> | 98% | 54,143 psi | 85% | 3077 fps | 99.1% |
| Norma URP | <<locked>> | 92% | 55,622 psi | 87% | 3002 fps | 100% |
| Ramshot Big Game | <<locked>> | 84% | 57,101 psi | 89% | 2995 fps | 100% |
| Ramshot Grandᴾ | <<locked>> | 100% | 53,214 psi | 83% | 3035 fps | 96.9% |
| Ramshot Hunter | <<locked>> | 92% | 54,302 psi | 85% | 2999 fps | 99.6% |
| Ramshot Magnumᴾ | <<locked>> | 100% | 47,529 psi | 74% | 2907 fps | 97.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,028 psi | 58% | 1886 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 84% | 54,331 psi | 85% | 2923 fps | 99.4% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 54,505 psi | 85% | 3031 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 56,681 psi | 89% | 3035 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 55,230 psi | 87% | 3068 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 43,714 psi | 69% | 2920 fps | 97.4% |
| Rottweil R 902 | <<locked>> | 84% | 57,566 psi | 90% | 2923 fps | 100% |
| Rottweil R 903 | <<locked>> | 88% | 57,711 psi | 90% | 2972 fps | 100% |
| Rottweil R 904 | <<locked>> | 96% | 55,825 psi | 87% | 2969 fps | 97.1% |
| Rottweil R 905 | <<locked>> | 98% | 56,405 psi | 88% | 3031 fps | 98.4% |
| Rottweil R 907 | <<locked>> | 90% | 56,913 psi | 89% | 2959 fps | 99% |
| Shooters World Long Rifle | <<locked>> | 90% | 55,376 psi | 87% | 2933 fps | 99.7% |
| Shooters World Precision | <<locked>> | 84% | 55,651 psi | 87% | 2913 fps | 100% |
| Shooters World SW4350 | <<locked>> | 92% | 56,797 psi | 89% | 2979 fps | 99.4% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 55,869 psi | 88% | 2982 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 56,811 psi | 89% | 2953 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 82% | 57,725 psi | 90% | 2851 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 55,201 psi | 87% | 2805 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 90% | 54,882 psi | 86% | 2884 fps | 99.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 98% | 55,912 psi | 88% | 3025 fps | 98.3% |
| Somchem S335 | <<locked>> | 82% | 57,348 psi | 90% | 2848 fps | 100% |
| Somchem S355 | <<locked>> | 88% | 57,580 psi | 90% | 2966 fps | 100% |
| Somchem S361 | <<locked>> | 94% | 53,983 psi | 85% | 2904 fps | 95.9% |
| Somchem S365 | <<locked>> | 94% | 54,911 psi | 86% | 3002 fps | 100% |
| Somchem S385 | <<locked>> | 98% | 57,232 psi | 90% | 3009 fps | 99% |
| Vihtavuori N135 | <<locked>> | 82% | 54,650 psi | 86% | 2835 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 54,853 psi | 86% | 2851 fps | 100% |
| Vihtavuori N150 | <<locked>> | 88% | 55,332 psi | 87% | 2890 fps | 100% |
| Vihtavuori N160 | <<locked>> | 92% | 57,667 psi | 90% | 2995 fps | 100% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 52,852 psi | 83% | 2927 fps | 98.2% |
| Vihtavuori N540 | <<locked>> | 84% | 56,463 psi | 88% | 2894 fps | 100% |
| Vihtavuori N550 | <<locked>> | 92% | 56,869 psi | 89% | 2999 fps | 100% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 57,464 psi | 90% | 3058 fps | 100% |
| Vihtavuori N560 | <<locked>> | 98% | 54,447 psi | 85% | 3064 fps | 96.4% |
| Winchester 6.5 StaBALL | <<locked>> | 92% | 57,290 psi | 90% | 2956 fps | 100% |
| Winchester 760 | <<locked>> | 90% | 55,405 psi | 87% | 3012 fps | 99.2% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 46,514 psi | 73% | 3041 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 82% | 56,840 psi | 89% | 2959 fps | 100% |
| Winchester Supreme 780ᴾ | <<locked>> | 100% | 57,450 psi | 90% | 3005 fps | 98.3% |
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 2495 | <<locked>> | 80% | 52,257 psi | 82% | 2802 fps | 100% |
| Accurate 2700 | <<locked>> | 80% | 49,632 psi | 78% | 2802 fps | 97.7% |
| Accurate 3100 | <<locked>> | 86% | 34,011 psi | 53% | 2559 fps | 95.1% |
| Accurate 4064 | <<locked>> | 80% | 49,516 psi | 78% | 2808 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 37,710 psi | 59% | 2667 fps | 98.1% |
| Accurate MAGPRO | <<locked>> | 98% | 53,084 psi | 83% | 3041 fps | 95.4% |
| ADI AR 2208 | <<locked>> | 80% | 46,398 psi | 73% | 2776 fps | 99.7% |
| ADI AR 2209 | <<locked>> | 90% | 44,599 psi | 70% | 2822 fps | 95.6% |
| ADI AR 2213 | <<locked>> | 96% | 48,544 psi | 76% | 2927 fps | 95.1% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 51,619 psi | 81% | 3002 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 47,065 psi | 74% | 2805 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 50,299 psi | 79% | 2874 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 80% | 36,724 psi | 58% | 2677 fps | 98.1% |
| Alliant Reloder-17 | 44.8 gr | 80% | 41,669 psi | 65% | 2805 fps | 99.9% |
| Alliant Reloder-19 | <<locked>> | 90% | 44,063 psi | 69% | 2812 fps | 95.6% |
| Alliant Reloder-22 | <<locked>> | 94% | 44,454 psi | 70% | 2861 fps | 95.8% |
| Alliant Reloder-23 | <<locked>> | 80% | 27,006 psi | 42% | 2421 fps | 95.7% |
| Alliant Reloder-25 | <<locked>> | 92% | 34,592 psi | 54% | 2657 fps | 95.9% |
| Alliant Reloder-26 | 48.2 gr | 84% | 33,098 psi | 52% | 2657 fps | 96.2% |
| Bofors RP15 | <<locked>> | 96% | 43,830 psi | 69% | 2848 fps | 95.5% |
| Bofors RP3 | <<locked>> | 80% | 47,268 psi | 74% | 2812 fps | 100% |
| Bofors RP5 | <<locked>> | 94% | 44,454 psi | 70% | 2861 fps | 95.8% |
| Bofors RP7 | <<locked>> | 80% | 41,698 psi | 65% | 2680 fps | 96% |
| Hodgdon H380 | <<locked>> | 80% | 47,718 psi | 75% | 2825 fps | 99.4% |
| Hodgdon H414 | <<locked>> | 80% | 39,610 psi | 62% | 2713 fps | 96% |
| Hodgdon H4350 | <<locked>> | 80% | 42,424 psi | 66% | 2733 fps | 95.4% |
| Hodgdon H4831 | <<locked>> | 96% | 51,895 psi | 81% | 2933 fps | 95.4% |
| Hodgdon H4831 SC | <<locked>> | 96% | 50,937 psi | 80% | 2913 fps | 95.1% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 34,229 psi | 54% | 2566 fps | 98.7% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 52,156 psi | 82% | 2923 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 98% | 41,104 psi | 64% | 2861 fps | 95.1% |
| Hodgdon Superformance | <<locked>> | 80% | 38,508 psi | 60% | 2717 fps | 95.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,267 psi | 43% | 1650 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 52,736 psi | 83% | 2884 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 48,805 psi | 76% | 2812 fps | 99.9% |
| IMR 4166 Enduron | <<locked>> | 80% | 51,140 psi | 80% | 2844 fps | 98.6% |
| IMR 4350 | <<locked>> | 82% | 39,784 psi | 62% | 2661 fps | 95.4% |
| IMR 4451 Enduron | <<locked>> | 80% | 43,134 psi | 68% | 2713 fps | 96.9% |
| IMR 4831 | <<locked>> | 80% | 36,187 psi | 57% | 2615 fps | 97.7% |
| IMR 4895 | <<locked>> | 80% | 51,547 psi | 81% | 2904 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 94% | 50,473 psi | 79% | 2871 fps | 95.3% |
| IMR 7828 SSC | <<locked>> | 98% | 49,385 psi | 77% | 2956 fps | 95.5% |
| Lovex S060 | <<locked>> | 80% | 53,417 psi | 84% | 2851 fps | 100% |
| Lovex S062 | <<locked>> | 80% | 49,095 psi | 77% | 2812 fps | 100% |
| Lovex S065 | <<locked>> | 80% | 40,741 psi | 64% | 2664 fps | 97.6% |
| Lovex S070 | <<locked>> | 80% | 38,812 psi | 61% | 2641 fps | 95.9% |
| Lovex S071 | <<locked>> | 92% | 35,085 psi | 55% | 2585 fps | 95.5% |
| Norma 201 | <<locked>> | 80% | 53,664 psi | 84% | 2874 fps | 100% |
| Norma 202 | <<locked>> | 80% | 54,172 psi | 85% | 2871 fps | 100% |
| Norma 203B | <<locked>> | 80% | 49,632 psi | 78% | 2861 fps | 100% |
| Norma 204 | <<locked>> | 86% | 45,150 psi | 71% | 2812 fps | 95.6% |
| Norma MRP | <<locked>> | 88% | 38,159 psi | 60% | 2753 fps | 95.3% |
| Norma URP | <<locked>> | 80% | 37,405 psi | 59% | 2657 fps | 97.9% |
| Ramshot Big Game | <<locked>> | 80% | 50,038 psi | 78% | 2884 fps | 100% |
| Ramshot Grand | <<locked>> | 98% | 49,545 psi | 78% | 2969 fps | 96% |
| Ramshot Hunter | <<locked>> | 80% | 36,390 psi | 57% | 2644 fps | 95.8% |
| Ramshot Magnum | <<locked>> | 96% | 41,176 psi | 65% | 2776 fps | 95.5% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,818 psi | 44% | 1693 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 47,732 psi | 75% | 2808 fps | 98.5% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 44,280 psi | 69% | 2861 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 37,376 psi | 59% | 2680 fps | 97.7% |
| ReloadSwiss RS 70 | 45.5 gr | 80% | 36,419 psi | 57% | 2687 fps | 97% |
| ReloadSwiss RS 76 | <<locked>> | 96% | 37,971 psi | 60% | 2776 fps | 95% |
| Rottweil R 902 | <<locked>> | 80% | 51,097 psi | 80% | 2825 fps | 100% |
| Rottweil R 903 | <<locked>> | 80% | 44,599 psi | 70% | 2759 fps | 100% |
| Rottweil R 904 | <<locked>> | 92% | 49,197 psi | 77% | 2854 fps | 95.6% |
| Rottweil R 905 | <<locked>> | 90% | 43,308 psi | 68% | 2795 fps | 95.5% |
| Rottweil R 907 | <<locked>> | 80% | 41,698 psi | 65% | 2680 fps | 96% |
| Shooters World Long Rifle | <<locked>> | 80% | 40,741 psi | 64% | 2664 fps | 97.6% |
| Shooters World Precision | <<locked>> | 80% | 49,095 psi | 77% | 2812 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 38,812 psi | 61% | 2641 fps | 95.9% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 45,832 psi | 72% | 2815 fps | 99.9% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 53,258 psi | 83% | 2900 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 54,288 psi | 85% | 2805 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 45,963 psi | 72% | 2667 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 39,842 psi | 62% | 2605 fps | 96.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 90% | 42,917 psi | 67% | 2792 fps | 95.4% |
| Somchem S335 | <<locked>> | 80% | 54,114 psi | 85% | 2802 fps | 100% |
| Somchem S355 | <<locked>> | 80% | 45,020 psi | 71% | 2762 fps | 100% |
| Somchem S361 | <<locked>> | 92% | 50,575 psi | 79% | 2844 fps | 95% |
| Somchem S365 | <<locked>> | 80% | 34,026 psi | 53% | 2618 fps | 99.5% |
| Somchem S385 | <<locked>> | 88% | 41,205 psi | 65% | 2720 fps | 95.8% |
| Vihtavuori N135 | <<locked>> | 80% | 51,329 psi | 80% | 2789 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 51,358 psi | 80% | 2799 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 42,844 psi | 67% | 2687 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 38,885 psi | 61% | 2661 fps | 98.2% |
| Vihtavuori N165 | <<locked>> | 92% | 40,451 psi | 63% | 2697 fps | 95.1% |
| Vihtavuori N540 | <<locked>> | 80% | 49,647 psi | 78% | 2792 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 38,305 psi | 60% | 2657 fps | 97.9% |
| Vihtavuori N555 | <<locked>> | 80% | 29,747 psi | 47% | 2500 fps | 95.9% |
| Vihtavuori N560 | <<locked>> | 96% | 50,589 psi | 79% | 2992 fps | 95.4% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 37,927 psi | 59% | 2628 fps | 99.6% |
| Winchester 760 | <<locked>> | 80% | 39,610 psi | 62% | 2713 fps | 96% |
| Winchester StaBALL HD | <<locked>> | 82% | 25,440 psi | 40% | 2444 fps | 95.2% |
| Winchester StaBALL Match | <<locked>> | 80% | 53,258 psi | 83% | 2907 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 92% | 43,352 psi | 68% | 2759 fps | 95.3% |
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 96 powders for .255 GS loaded with the .257 | 117gr | Sellier & Bellot SPFN. Alliant Reloder-26 delivers the highest muzzle velocity at 3,123 fps; across all powders the maximum-charge window runs from 1,847 fps to 3,123 fps. Accurate 3100 gives the best case fill at 100 %, and 96 of the 96 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 57–90 %, leaving at least 10 % headroom. The 117.0 gr projectile in 0.257" calls for a 1:13.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, Accurate MAGPRO, ADI AR 2213 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 70, Alliant Reloder-26, Alliant Reloder-17 rank at the top here: for .255 GS with the .257 | 117gr | Sellier & Bellot SPFN 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.