Load Specifications
Bullet Manufacturer:Sierra
Bullet Weight:100 gr
Bullet Diameter:0.257"
Bullet Length:<<locked>>
Caliber:.25 Creedmoor load data
Case Length (l3):1.92"
Cartridge Length (C.O.L.):<<locked>>
Case Capacity:51.5 Grains of Water
Primer Size:Large Rifle (LR)
Barrel Length:24"
Max. allowed Pressure:62,001 psi
Recommended Twist Rate:1:11.5
Load data in caliber .25 Creedmoor with .257 | 100gr | Sierra GameKing bullet and 95 powders. The key underlying parameters are shown in the table above.
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% | 55,463 psi | 89% | 2963 fps | 100% |
| Accurate 2460 | <<locked>> | 82% | 53,824 psi | 87% | 2982 fps | 100% |
| Accurate 2495 | <<locked>> | 90% | 53,838 psi | 87% | 2982 fps | 100% |
| Accurate 2520 | <<locked>> | 86% | 56,072 psi | 90% | 3054 fps | 100% |
| Accurate 4064 | <<locked>> | 92% | 53,896 psi | 87% | 3028 fps | 100% |
| Accurate 4350ᴾ | <<locked>> | 100% | 53,156 psi | 86% | 3094 fps | 98.8% |
| ADI AR 2206H | <<locked>> | 88% | 54,752 psi | 88% | 3061 fps | 99.6% |
| ADI AR 2208 | <<locked>> | 94% | 55,535 psi | 90% | 3051 fps | 99.3% |
| ADI Benchmark 8208 | <<locked>> | 86% | 53,795 psi | 87% | 3012 fps | 99.9% |
| Alliant AR-Comp | <<locked>> | 86% | 53,998 psi | 87% | 2992 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 82% | 55,434 psi | 89% | 3123 fps | 99.9% |
| Alliant Power Pro 2000-MR | <<locked>> | 90% | 54,259 psi | 88% | 3176 fps | 99.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 94% | 55,506 psi | 90% | 3081 fps | 99.9% |
| Alliant Reloder-10x | <<locked>> | 82% | 54,998 psi | 89% | 2966 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 90% | 52,794 psi | 85% | 3048 fps | 99.2% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 51,619 psi | 83% | 3097 fps | 98.9% |
| Alliant Reloder-17 | <<locked>> | 96% | 52,794 psi | 85% | 3143 fps | 99.8% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 36,796 psi | 59% | 2802 fps | 96.7% |
| Baschieri & Pellagri 107 | <<locked>> | 88% | 54,607 psi | 88% | 3071 fps | 99.1% |
| Bofors RP3 | <<locked>> | 94% | 56,043 psi | 90% | 3094 fps | 100% |
| Hodgdon Benchmark | <<locked>> | 86% | 55,622 psi | 90% | 2995 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 86% | 52,968 psi | 85% | 3038 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 84% | 54,897 psi | 89% | 3140 fps | 99.4% |
| Hodgdon H322 | <<locked>> | 82% | 54,462 psi | 88% | 3012 fps | 100% |
| Hodgdon H335 | <<locked>> | 82% | 55,419 psi | 89% | 3035 fps | 100% |
| Hodgdon H380 | <<locked>> | 92% | 53,824 psi | 87% | 3051 fps | 98.4% |
| Hodgdon H414 | <<locked>> | 98% | 52,924 psi | 85% | 3087 fps | 96.4% |
| Hodgdon H4895 | <<locked>> | 88% | 55,259 psi | 89% | 3071 fps | 99.8% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 47,732 psi | 77% | 2969 fps | 99.2% |
| Hodgdon LEVERevolution | <<locked>> | 90% | 54,505 psi | 88% | 3104 fps | 99.9% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 34,998 psi | 56% | 1877 fps | 100% |
| Hodgdon VARGET | <<locked>> | 88% | 53,258 psi | 86% | 3022 fps | 99.7% |
| IMR 3031 | <<locked>> | 88% | 55,042 psi | 89% | 3061 fps | 100% |
| IMR 4064 | <<locked>> | 92% | 55,288 psi | 89% | 3038 fps | 99.4% |
| IMR 4166 Enduron | <<locked>> | 90% | 55,593 psi | 90% | 3015 fps | 96.7% |
| IMR 4198 | <<locked>> | 82% | 55,071 psi | 89% | 2927 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 96% | 54,781 psi | 88% | 3028 fps | 96.5% |
| IMR 4831ᴾ | <<locked>> | 100% | 50,705 psi | 82% | 3031 fps | 98.5% |
| IMR 4895 | <<locked>> | 90% | 54,128 psi | 87% | 3081 fps | 99.6% |
| IMR 8208 XBR | <<locked>> | 86% | 53,795 psi | 87% | 3012 fps | 99.9% |
| Lovex D073.5 | <<locked>> | 82% | 54,012 psi | 87% | 2995 fps | 100% |
| Lovex D073.6 | <<locked>> | 88% | 54,302 psi | 88% | 3035 fps | 100% |
| Lovex S060 | <<locked>> | 88% | 54,433 psi | 88% | 2982 fps | 99.6% |
| Lovex S062 | <<locked>> | 92% | 55,042 psi | 89% | 3038 fps | 100% |
| Lovex S065 | <<locked>> | 98% | 54,085 psi | 87% | 3025 fps | 97.8% |
| Lovex S070ᴾ | <<locked>> | 100% | 55,027 psi | 89% | 3061 fps | 96.9% |
| Norma 201 | <<locked>> | 88% | 53,316 psi | 86% | 3002 fps | 99.9% |
| Norma 202 | <<locked>> | 88% | 53,766 psi | 87% | 3005 fps | 100% |
| Norma 203B | <<locked>> | 92% | 55,405 psi | 89% | 3091 fps | 99.7% |
| Norma URPᴾ | <<locked>> | 100% | 52,678 psi | 85% | 3084 fps | 98.7% |
| Ramshot Big Game | <<locked>> | 90% | 52,286 psi | 84% | 3054 fps | 99.3% |
| Ramshot Hunterᴾ | <<locked>> | 100% | 51,561 psi | 83% | 3071 fps | 97% |
| Ramshot TAC | <<locked>> | 86% | 54,230 psi | 87% | 3022 fps | 98% |
| Ramshot Wild Boar | <<locked>> | 86% | 53,519 psi | 86% | 3041 fps | 99.5% |
| Ramshot X-Terminator | <<locked>> | 84% | 54,694 psi | 88% | 3009 fps | 99.5% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,447 psi | 57% | 1919 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 82% | 53,171 psi | 86% | 2992 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 92% | 54,012 psi | 87% | 3025 fps | 97.1% |
| ReloadSwiss RS 52 | <<locked>> | 88% | 52,881 psi | 85% | 3110 fps | 99.2% |
| ReloadSwiss RS 60 | <<locked>> | 94% | 52,359 psi | 84% | 3146 fps | 100% |
| ReloadSwiss RS 62ᴾ | <<locked>> | 100% | 53,113 psi | 86% | 3117 fps | 98.6% |
| ReloadSwiss RS 70ᴾ | <<locked>> | 100% | 53,432 psi | 86% | 3143 fps | 98.3% |
| Rottweil R 901 | <<locked>> | 86% | 54,534 psi | 88% | 2992 fps | 100% |
| Rottweil R 902 | <<locked>> | 90% | 53,766 psi | 87% | 2999 fps | 99.9% |
| Rottweil R 903 | <<locked>> | 96% | 55,883 psi | 90% | 3084 fps | 99.9% |
| Shooters World Long Rifle | <<locked>> | 98% | 54,085 psi | 87% | 3025 fps | 97.8% |
| Shooters World Match Rifle | <<locked>> | 88% | 54,302 psi | 88% | 3035 fps | 100% |
| Shooters World Precision | <<locked>> | 92% | 55,042 psi | 89% | 3038 fps | 100% |
| Shooters World SW4350ᴾ | <<locked>> | 100% | 55,027 psi | 89% | 3061 fps | 96.9% |
| SNPE Vectan SP 11 | <<locked>> | 94% | 53,998 psi | 87% | 3087 fps | 99.5% |
| SNPE Vectan SP 3 | <<locked>> | 82% | 55,985 psi | 90% | 2992 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 88% | 55,999 psi | 90% | 3051 fps | 98.6% |
| SNPE Vectan SP 9 | <<locked>> | 88% | 53,243 psi | 86% | 3028 fps | 99.5% |
| SNPE Vectan Tubal 3000 | <<locked>> | 88% | 55,347 psi | 89% | 2953 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 94% | 55,288 psi | 89% | 2943 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 98% | 54,491 psi | 88% | 2972 fps | 96.5% |
| Somchem S321 | <<locked>> | 84% | 55,230 psi | 89% | 3048 fps | 100% |
| Somchem S335 | <<locked>> | 88% | 54,346 psi | 88% | 2943 fps | 100% |
| Somchem S341 | <<locked>> | 88% | 55,753 psi | 90% | 3048 fps | 99.6% |
| Somchem S355 | <<locked>> | 96% | 56,101 psi | 90% | 3077 fps | 99.9% |
| Somchem S365ᴾ | <<locked>> | 100% | 46,949 psi | 76% | 3028 fps | 99.9% |
| Vihtavuori N130 | <<locked>> | 84% | 55,027 psi | 89% | 2917 fps | 100% |
| Vihtavuori N133 | <<locked>> | 88% | 55,448 psi | 89% | 2936 fps | 100% |
| Vihtavuori N135 | <<locked>> | 90% | 53,359 psi | 86% | 2969 fps | 100% |
| Vihtavuori N140 | <<locked>> | 90% | 54,259 psi | 88% | 2986 fps | 100% |
| Vihtavuori N150 | <<locked>> | 96% | 54,302 psi | 88% | 3009 fps | 100% |
| Vihtavuori N160ᴾ | <<locked>> | 100% | 55,027 psi | 89% | 3081 fps | 98.9% |
| Vihtavuori N530 | <<locked>> | 86% | 54,244 psi | 87% | 3012 fps | 100% |
| Vihtavuori N540 | <<locked>> | 90% | 52,866 psi | 85% | 2982 fps | 100% |
| Vihtavuori N550ᴾ | <<locked>> | 100% | 54,215 psi | 87% | 3084 fps | 98.7% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 39,711 psi | 64% | 2884 fps | 96.7% |
| Winchester 6.5 StaBALLᴾ | <<locked>> | 100% | 55,927 psi | 90% | 3061 fps | 99.9% |
| Winchester 748 | <<locked>> | 86% | 54,027 psi | 87% | 3061 fps | 100% |
| Winchester 760 | <<locked>> | 98% | 52,924 psi | 85% | 3087 fps | 96.4% |
| Winchester StaBALL Match | <<locked>> | 88% | 52,823 psi | 85% | 3031 fps | 99.7% |
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 80% | 46,267 psi | 75% | 2818 fps | 100% |
| Accurate 2460 | <<locked>> | 80% | 50,502 psi | 81% | 2930 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 38,638 psi | 62% | 2723 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 45,716 psi | 74% | 2887 fps | 99.9% |
| Accurate 4064 | <<locked>> | 80% | 36,550 psi | 59% | 2707 fps | 99.6% |
| Accurate 4350 | <<locked>> | 90% | 37,608 psi | 61% | 2789 fps | 95.1% |
| ADI AR 2206H | <<locked>> | 80% | 42,409 psi | 68% | 2828 fps | 97.8% |
| ADI AR 2208 | <<locked>> | 80% | 36,216 psi | 58% | 2667 fps | 95.3% |
| ADI Benchmark 8208 | <<locked>> | 80% | 44,440 psi | 72% | 2844 fps | 99.1% |
| Alliant AR-Comp | <<locked>> | 80% | 44,150 psi | 71% | 2841 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 80% | 51,808 psi | 84% | 3061 fps | 99.6% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 38,319 psi | 62% | 2838 fps | 95.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 35,462 psi | 57% | 2687 fps | 96.9% |
| Alliant Reloder-10x | <<locked>> | 80% | 51,895 psi | 84% | 2920 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 38,203 psi | 62% | 2753 fps | 96.2% |
| Alliant Reloder-16 | <<locked>> | 90% | 37,710 psi | 61% | 2799 fps | 95.1% |
| Alliant Reloder-17 | <<locked>> | 82% | 32,822 psi | 53% | 2697 fps | 95% |
| Alliant Reloder-23 | <<locked>> | 98% | 34,519 psi | 56% | 2740 fps | 95.7% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 41,466 psi | 67% | 2825 fps | 96.5% |
| Bofors RP3 | <<locked>> | 80% | 35,027 psi | 56% | 2687 fps | 96.9% |
| Hodgdon Benchmark | <<locked>> | 80% | 46,456 psi | 75% | 2841 fps | 99.7% |
| Hodgdon BL-C2 | <<locked>> | 80% | 43,018 psi | 69% | 2858 fps | 99.3% |
| Hodgdon CFE223 | <<locked>> | 80% | 47,340 psi | 76% | 3005 fps | 98.4% |
| Hodgdon H322 | <<locked>> | 80% | 50,966 psi | 82% | 2959 fps | 100% |
| Hodgdon H335 | <<locked>> | 80% | 51,967 psi | 84% | 2982 fps | 100% |
| Hodgdon H380 | <<locked>> | 84% | 41,133 psi | 66% | 2808 fps | 95.6% |
| Hodgdon H414 | <<locked>> | 96% | 49,530 psi | 80% | 3028 fps | 95.6% |
| Hodgdon H4895 | <<locked>> | 80% | 42,801 psi | 69% | 2841 fps | 98.4% |
| Hodgdon Hybrid 100V | <<locked>> | 88% | 32,518 psi | 52% | 2631 fps | 95.1% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 38,682 psi | 62% | 2802 fps | 97.9% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,034 psi | 42% | 1677 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 41,118 psi | 66% | 2792 fps | 98% |
| IMR 3031 | <<locked>> | 80% | 42,148 psi | 68% | 2848 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 37,971 psi | 61% | 2707 fps | 96.2% |
| IMR 4166 Enduron | <<locked>> | 86% | 49,023 psi | 79% | 2900 fps | 95.2% |
| IMR 4198 | <<locked>> | 80% | 51,909 psi | 84% | 2881 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 92% | 48,689 psi | 79% | 2923 fps | 95% |
| IMR 4831 | <<locked>> | 92% | 38,769 psi | 63% | 2795 fps | 95.7% |
| IMR 4895 | <<locked>> | 80% | 39,131 psi | 63% | 2789 fps | 97.1% |
| IMR 8208 XBR | <<locked>> | 80% | 44,440 psi | 72% | 2844 fps | 99.1% |
| Lovex D073.5 | <<locked>> | 80% | 50,256 psi | 81% | 2936 fps | 100% |
| Lovex D073.6 | <<locked>> | 80% | 41,365 psi | 67% | 2812 fps | 99.6% |
| Lovex S060 | <<locked>> | 80% | 42,583 psi | 69% | 2766 fps | 97.9% |
| Lovex S062 | <<locked>> | 80% | 37,637 psi | 61% | 2707 fps | 97.9% |
| Lovex S065 | <<locked>> | 90% | 42,279 psi | 68% | 2802 fps | 95% |
| Lovex S070 | <<locked>> | 96% | 48,443 psi | 78% | 2943 fps | 95.4% |
| Norma 201 | <<locked>> | 80% | 41,495 psi | 67% | 2782 fps | 98.7% |
| Norma 202 | <<locked>> | 80% | 41,698 psi | 67% | 2795 fps | 99.9% |
| Norma 203B | <<locked>> | 80% | 37,594 psi | 61% | 2743 fps | 96.6% |
| Norma URP | <<locked>> | 90% | 37,782 psi | 61% | 2789 fps | 95% |
| Ramshot Big Game | <<locked>> | 80% | 36,970 psi | 60% | 2749 fps | 96.2% |
| Ramshot Hunter | <<locked>> | 96% | 45,353 psi | 73% | 2953 fps | 95.4% |
| Ramshot TAC | <<locked>> | 80% | 44,440 psi | 72% | 2841 fps | 95.8% |
| Ramshot Wild Boar | <<locked>> | 80% | 43,961 psi | 71% | 2867 fps | 98.1% |
| Ramshot X-Terminator | <<locked>> | 80% | 48,080 psi | 78% | 2894 fps | 98.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,513 psi | 43% | 1722 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 80% | 49,893 psi | 80% | 2936 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 88% | 47,601 psi | 77% | 2910 fps | 95.6% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 39,871 psi | 64% | 2858 fps | 96.6% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 32,750 psi | 53% | 2710 fps | 97.7% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 39,972 psi | 64% | 2864 fps | 95.6% |
| ReloadSwiss RS 70 | <<locked>> | 94% | 43,337 psi | 70% | 2940 fps | 95.7% |
| Rottweil R 901 | <<locked>> | 80% | 45,397 psi | 73% | 2838 fps | 100% |
| Rottweil R 902 | <<locked>> | 80% | 39,508 psi | 64% | 2730 fps | 98.3% |
| Rottweil R 903 | <<locked>> | 80% | 32,895 psi | 53% | 2625 fps | 95.7% |
| Shooters World Long Rifle | <<locked>> | 90% | 42,279 psi | 68% | 2802 fps | 95% |
| Shooters World Match Rifle | <<locked>> | 80% | 41,365 psi | 67% | 2812 fps | 99.6% |
| Shooters World Precision | <<locked>> | 80% | 37,637 psi | 61% | 2707 fps | 97.9% |
| Shooters World SW4350 | <<locked>> | 96% | 48,443 psi | 78% | 2943 fps | 95.4% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 34,040 psi | 55% | 2680 fps | 95.1% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 52,750 psi | 85% | 2943 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 42,569 psi | 69% | 2812 fps | 95.9% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 41,046 psi | 66% | 2795 fps | 97.5% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 43,120 psi | 70% | 2746 fps | 99.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 35,723 psi | 58% | 2602 fps | 99.7% |
| SNPE Vectan Tubal 7000 | <<locked>> | 94% | 47,993 psi | 77% | 2864 fps | 95% |
| Somchem S321 | <<locked>> | 80% | 47,979 psi | 77% | 2927 fps | 99.7% |
| Somchem S335 | <<locked>> | 80% | 42,496 psi | 69% | 2746 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 42,279 psi | 68% | 2808 fps | 97.7% |
| Somchem S355 | <<locked>> | 80% | 33,823 psi | 55% | 2635 fps | 95.8% |
| Somchem S365 | <<locked>> | 86% | 29,776 psi | 48% | 2615 fps | 95.5% |
| Vihtavuori N130 | <<locked>> | 80% | 48,718 psi | 79% | 2822 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 43,366 psi | 70% | 2746 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 38,885 psi | 63% | 2726 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 39,494 psi | 64% | 2726 fps | 99.8% |
| Vihtavuori N150 | <<locked>> | 80% | 32,155 psi | 52% | 2572 fps | 96.8% |
| Vihtavuori N160 | <<locked>> | 90% | 39,740 psi | 64% | 2795 fps | 95.6% |
| Vihtavuori N530 | <<locked>> | 80% | 44,541 psi | 72% | 2841 fps | 99.2% |
| Vihtavuori N540 | <<locked>> | 80% | 38,174 psi | 62% | 2713 fps | 99.5% |
| Vihtavuori N550 | <<locked>> | 90% | 39,189 psi | 63% | 2799 fps | 95.2% |
| Vihtavuori N555 | <<locked>> | 98% | 37,101 psi | 60% | 2825 fps | 95.8% |
| Winchester 6.5 StaBALL | <<locked>> | 84% | 32,938 psi | 53% | 2598 fps | 95.4% |
| Winchester 748 | <<locked>> | 80% | 44,048 psi | 71% | 2887 fps | 99.6% |
| Winchester 760 | <<locked>> | 96% | 49,530 psi | 80% | 3028 fps | 95.6% |
| Winchester StaBALL Match | <<locked>> | 80% | 40,509 psi | 65% | 2802 fps | 98% |
ᴾ possible press load - work up slowly to this load while watching for signs of excessive pressure.
This overview compares 111 powders for .25 Creedmoor loaded with the .257 | 100gr | Sierra GameKing. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,176 fps; across all powders the maximum-charge window runs from 1,877 fps to 3,176 fps. Accurate 3100 gives the best case fill at 100 %, and 111 of the 111 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (427 MPa), the top charges use 53–90 %, leaving at least 10 % headroom. The 100.0 gr projectile in 0.257" calls for a 1:11.5 twist; slower twists will usually not stabilise this weight. Accurate 3100, Accurate 4350, ADI AR 2209 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. 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.