Load Specifications
Load data in caliber .257 Roberts with .257 | 100gr | Winchester Silvertip bullet and 49 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 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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Max Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2495 | <<locked>> | 82% | 44,034 psi | 86% | 2848 fps | 100% |
| Accurate 4064 | <<locked>> | 84% | 44,280 psi | 86% | 2890 fps | 100% |
| Accurate 4350 | <<locked>> | 94% | 46,296 psi | 90% | 2999 fps | 97.9% |
| ADI AR 2208 | <<locked>> | 86% | 45,716 psi | 89% | 2907 fps | 98.2% |
| Alliant Power Pro 2000-MR | <<locked>> | 84% | 46,456 psi | 90% | 3058 fps | 98.4% |
| Alliant Reloder- TS 15.5 | <<locked>> | 86% | 45,382 psi | 88% | 2933 fps | 99.3% |
| Alliant Reloder-15 | <<locked>> | 84% | 45,730 psi | 89% | 2946 fps | 98.4% |
| Alliant Reloder-16 | <<locked>> | 94% | 45,092 psi | 88% | 3002 fps | 98% |
| Alliant Reloder-17 | <<locked>> | 90% | 45,585 psi | 89% | 3038 fps | 99.3% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 39,001 psi | 76% | 2887 fps | 97.9% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 43,700 psi | 85% | 3054 fps | 97% |
| Bofors RP3 | <<locked>> | 86% | 45,382 psi | 88% | 2940 fps | 99.4% |
| Hodgdon H380 | <<locked>> | 86% | 46,514 psi | 90% | 2949 fps | 97.5% |
| Hodgdon Hybrid 100V | <<locked>> | 96% | 44,686 psi | 87% | 2943 fps | 99% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 43,859 psi | 85% | 2940 fps | 99.2% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,433 psi | 69% | 1916 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 46,122 psi | 90% | 2923 fps | 99.1% |
| IMR 4064 | <<locked>> | 84% | 45,208 psi | 88% | 2890 fps | 98.3% |
| IMR 4831 | <<locked>> | 94% | 44,150 psi | 86% | 2936 fps | 97.6% |
| IMR 4895 | <<locked>> | 82% | 44,077 psi | 86% | 2923 fps | 98.5% |
| Lovex S062 | <<locked>> | 84% | 45,136 psi | 88% | 2897 fps | 99.5% |
| Lovex S065 | <<locked>> | 90% | 44,643 psi | 87% | 2884 fps | 96.1% |
| Norma 203B | <<locked>> | 84% | 45,034 psi | 87% | 2933 fps | 98.7% |
| Norma URP | <<locked>> | 94% | 45,919 psi | 89% | 2989 fps | 97.8% |
| Ramshot Big Game | <<locked>> | 84% | 44,947 psi | 87% | 2949 fps | 98.5% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,868 psi | 70% | 1959 fps | 100% |
| ReloadSwiss RS 52 | <<locked>> | 82% | 45,629 psi | 89% | 3005 fps | 98.3% |
| ReloadSwiss RS 60 | <<locked>> | 88% | 45,368 psi | 88% | 3048 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 94% | 45,890 psi | 89% | 3012 fps | 97.6% |
| ReloadSwiss RS 70 | <<locked>> | 94% | 45,934 psi | 89% | 3031 fps | 97% |
| Rottweil R 902 | <<locked>> | 82% | 44,237 psi | 86% | 2858 fps | 99.3% |
| Rottweil R 903 | <<locked>> | 88% | 45,614 psi | 89% | 2936 fps | 99.2% |
| Shooters World Long Rifle | <<locked>> | 90% | 44,643 psi | 87% | 2884 fps | 96.1% |
| Shooters World Precision | <<locked>> | 84% | 45,136 psi | 88% | 2897 fps | 99.5% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 43,888 psi | 85% | 2933 fps | 98.4% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 46,108 psi | 90% | 2930 fps | 98.8% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 45,281 psi | 88% | 2815 fps | 100% |
| Somchem S355 | <<locked>> | 88% | 46,093 psi | 90% | 2936 fps | 99.2% |
| Somchem S365 | <<locked>> | 96% | 43,947 psi | 85% | 2995 fps | 99.8% |
| Vihtavuori N135 | <<locked>> | 82% | 43,772 psi | 85% | 2841 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 44,498 psi | 86% | 2851 fps | 100% |
| Vihtavuori N150 | <<locked>> | 88% | 44,324 psi | 86% | 2867 fps | 99.6% |
| Vihtavuori N160 | <<locked>> | 92% | 44,904 psi | 87% | 2930 fps | 97.4% |
| Vihtavuori N540 | <<locked>> | 84% | 45,672 psi | 89% | 2887 fps | 100% |
| Vihtavuori N550 | <<locked>> | 92% | 44,367 psi | 86% | 2933 fps | 97.1% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 42,612 psi | 83% | 2969 fps | 97.8% |
| Winchester 6.5 StaBALL | <<locked>> | 92% | 45,324 psi | 88% | 2913 fps | 99.3% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 35,012 psi | 68% | 2871 fps | 97.3% |
| Winchester StaBALL Match | <<locked>> | 82% | 45,571 psi | 89% | 2930 fps | 99.1% |
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% | 41,017 psi | 80% | 2792 fps | 100% |
| Accurate 4064 | <<locked>> | 80% | 38,769 psi | 75% | 2779 fps | 99.9% |
| Accurate 4350 | <<locked>> | 88% | 37,405 psi | 73% | 2808 fps | 95.5% |
| ADI AR 2208 | <<locked>> | 80% | 37,797 psi | 73% | 2736 fps | 96.2% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 40,509 psi | 79% | 2923 fps | 96.8% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 37,449 psi | 73% | 2759 fps | 97.8% |
| Alliant Reloder-15 | <<locked>> | 80% | 40,451 psi | 79% | 2831 fps | 97.2% |
| Alliant Reloder-16 | 40.7 gr | 88% | 37,579 psi | 73% | 2825 fps | 95.6% |
| Alliant Reloder-17 | 39.8 gr | 80% | 32,416 psi | 63% | 2713 fps | 95.3% |
| Alliant Reloder-23 | <<locked>> | 94% | 32,329 psi | 63% | 2707 fps | 95.2% |
| Alliant Reloder-26 | <<locked>> | 98% | 40,756 psi | 79% | 2982 fps | 96% |
| Bofors RP3 | <<locked>> | 80% | 37,260 psi | 72% | 2766 fps | 97.8% |
| Hodgdon H380 | <<locked>> | 80% | 38,116 psi | 74% | 2766 fps | 95% |
| Hodgdon Hybrid 100V | <<locked>> | 86% | 32,387 psi | 63% | 2654 fps | 95.5% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 40,901 psi | 79% | 2877 fps | 98.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,353 psi | 51% | 1713 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 43,091 psi | 84% | 2861 fps | 98.7% |
| IMR 4064 | <<locked>> | 80% | 39,682 psi | 77% | 2776 fps | 97.1% |
| IMR 4831 | <<locked>> | 88% | 36,274 psi | 70% | 2762 fps | 95.2% |
| IMR 4895 | <<locked>> | 80% | 41,423 psi | 80% | 2867 fps | 98% |
| Lovex S062 | <<locked>> | 80% | 39,682 psi | 77% | 2782 fps | 98.6% |
| Lovex S065 | <<locked>> | 88% | 41,785 psi | 81% | 2822 fps | 95.3% |
| Norma 203B | <<locked>> | 80% | 39,813 psi | 77% | 2822 fps | 97.6% |
| Norma URP | <<locked>> | 88% | 37,724 psi | 73% | 2812 fps | 95.4% |
| Ramshot Big Game | <<locked>> | 80% | 39,160 psi | 76% | 2825 fps | 97.2% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,556 psi | 52% | 1752 fps | 100% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 42,438 psi | 82% | 2940 fps | 97.6% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 34,490 psi | 67% | 2789 fps | 98.7% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 37,159 psi | 72% | 2825 fps | 95% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 40,161 psi | 78% | 2900 fps | 95.1% |
| Rottweil R 902 | <<locked>> | 80% | 41,611 psi | 81% | 2805 fps | 99% |
| Rottweil R 903 | <<locked>> | 80% | 34,882 psi | 68% | 2700 fps | 96.8% |
| Shooters World Long Rifle | <<locked>> | 88% | 41,785 psi | 81% | 2822 fps | 95.3% |
| Shooters World Precision | <<locked>> | 80% | 39,682 psi | 77% | 2782 fps | 98.6% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 35,955 psi | 70% | 2753 fps | 96.2% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 43,134 psi | 84% | 2867 fps | 98.3% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 37,463 psi | 73% | 2664 fps | 99.9% |
| Somchem S355 | <<locked>> | 80% | 35,752 psi | 69% | 2710 fps | 96.9% |
| Somchem S365 | 39.6 gr | 84% | 29,530 psi | 57% | 2631 fps | 95.8% |
| Vihtavuori N135 | <<locked>> | 80% | 41,031 psi | 80% | 2789 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 41,510 psi | 81% | 2792 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 33,953 psi | 66% | 2641 fps | 97.7% |
| Vihtavuori N160 | <<locked>> | 86% | 36,941 psi | 72% | 2756 fps | 95.1% |
| Vihtavuori N540 | <<locked>> | 80% | 40,219 psi | 78% | 2782 fps | 99.8% |
| Vihtavuori N550 | <<locked>> | 88% | 38,986 psi | 76% | 2818 fps | 95.6% |
| Vihtavuori N555 | <<locked>> | 94% | 34,882 psi | 68% | 2792 fps | 95.3% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 32,460 psi | 63% | 2615 fps | 95.7% |
| Winchester StaBALL HD | <<locked>> | 98% | 32,750 psi | 64% | 2795 fps | 95.9% |
| Winchester StaBALL Match | <<locked>> | 80% | 42,598 psi | 83% | 2871 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 49 powders for .257 Roberts loaded with the .257 | 100gr | Winchester Silvertip. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,058 fps; across all powders the maximum-charge window runs from 1,916 fps to 3,058 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 49 of the 49 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (355 MPa), the top charges use 68–90 %, 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. Alliant Reloder-23, Alliant Reloder-26, Hodgdon TrailBoss 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, Alliant Reloder-17 rank at the top here: for .257 Roberts with the .257 | 100gr | Winchester Silvertip 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.