Load Specifications
Load data in caliber .257 Roberts with .257 | 117gr | Sellier & Bellot SPFN bullet and 46 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Norma MRP, Alliant Reloder-26 and Vihtavuori N555.
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 3100 | <<locked>> | 98% | 45,295 psi | 88% | 2762 fps | 97.8% |
| Accurate 4350 | <<locked>> | 88% | 44,382 psi | 86% | 2766 fps | 99% |
| ADI AR 2208 | <<locked>> | 82% | 45,426 psi | 88% | 2710 fps | 99.4% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 45,600 psi | 89% | 2733 fps | 99.9% |
| Alliant Reloder-16 | <<locked>> | 90% | 45,716 psi | 89% | 2825 fps | 99.4% |
| Alliant Reloder-17 | <<locked>> | 86% | 45,919 psi | 89% | 2848 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 45,629 psi | 89% | 2841 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 39,769 psi | 77% | 2740 fps | 97.1% |
| Alliant Reloder-26 | <<locked>> | 96% | 44,643 psi | 87% | 2894 fps | 99% |
| Bofors RP3 | <<locked>> | 82% | 45,876 psi | 89% | 2746 fps | 100% |
| Bofors RP7 | <<locked>> | 86% | 45,992 psi | 89% | 2720 fps | 96.4% |
| Hodgdon H380 | <<locked>> | 82% | 46,340 psi | 90% | 2753 fps | 98.9% |
| Hodgdon H414 | <<locked>> | 86% | 43,685 psi | 85% | 2756 fps | 96.5% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 45,397 psi | 88% | 2756 fps | 99.9% |
| Hodgdon Superformance | <<locked>> | 88% | 45,992 psi | 89% | 2828 fps | 96.7% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,926 psi | 70% | 1785 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 43,714 psi | 85% | 2697 fps | 95.8% |
| IMR 4451 Enduron | <<locked>> | 84% | 44,962 psi | 87% | 2700 fps | 96.6% |
| IMR 4831 | <<locked>> | 90% | 45,034 psi | 87% | 2762 fps | 99.1% |
| Lovex S065 | <<locked>> | 86% | 44,686 psi | 87% | 2700 fps | 97.9% |
| Lovex S070 | <<locked>> | 88% | 45,484 psi | 88% | 2733 fps | 97.1% |
| Lovex S071ᴾ | <<locked>> | 100% | 40,161 psi | 78% | 2664 fps | 96.6% |
| Norma MRP | <<locked>> | 96% | 44,527 psi | 86% | 2851 fps | 96.6% |
| Norma URP | <<locked>> | 88% | 43,801 psi | 85% | 2753 fps | 98.8% |
| Ramshot Hunter | <<locked>> | 90% | 45,455 psi | 88% | 2799 fps | 97.8% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,782 psi | 71% | 1831 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 45,585 psi | 89% | 2848 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 44,048 psi | 86% | 2782 fps | 98.7% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 46,035 psi | 89% | 2858 fps | 98.9% |
| Rottweil R 903 | <<locked>> | 84% | 46,050 psi | 89% | 2746 fps | 99.9% |
| Rottweil R 907 | <<locked>> | 86% | 45,992 psi | 89% | 2720 fps | 96.4% |
| Shooters World Long Rifle | <<locked>> | 86% | 44,686 psi | 87% | 2700 fps | 97.9% |
| Shooters World SW4350 | <<locked>> | 88% | 45,484 psi | 88% | 2733 fps | 97.1% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 44,396 psi | 86% | 2746 fps | 99.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 45,121 psi | 88% | 2615 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 44,222 psi | 86% | 2648 fps | 96.6% |
| Somchem S355 | <<locked>> | 84% | 46,572 psi | 90% | 2746 fps | 99.9% |
| Somchem S365 | <<locked>> | 92% | 45,150 psi | 88% | 2812 fps | 100% |
| Somchem S385 | <<locked>> | 94% | 44,715 psi | 87% | 2749 fps | 96.1% |
| Vihtavuori N150 | <<locked>> | 84% | 44,440 psi | 86% | 2674 fps | 100% |
| Vihtavuori N160 | <<locked>> | 88% | 45,788 psi | 89% | 2756 fps | 99% |
| Vihtavuori N550 | <<locked>> | 88% | 45,034 psi | 87% | 2756 fps | 98.8% |
| Vihtavuori N555 | <<locked>> | 96% | 44,585 psi | 87% | 2812 fps | 99.4% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 45,237 psi | 88% | 2726 fps | 100% |
| Winchester 760 | <<locked>> | 86% | 43,685 psi | 85% | 2756 fps | 96.5% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 41,017 psi | 80% | 2877 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 3100 | <<locked>> | 92% | 36,840 psi | 72% | 2592 fps | 95.5% |
| Accurate 4350 | <<locked>> | 80% | 33,504 psi | 65% | 2530 fps | 96.2% |
| ADI AR 2208 | <<locked>> | 80% | 42,757 psi | 83% | 2657 fps | 99% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 42,873 psi | 83% | 2684 fps | 99.8% |
| Alliant Reloder-16 | <<locked>> | 80% | 33,272 psi | 65% | 2539 fps | 96.2% |
| Alliant Reloder-17 | <<locked>> | 80% | 37,376 psi | 73% | 2671 fps | 99% |
| Alliant Reloder-23 | <<locked>> | 84% | 27,528 psi | 53% | 2402 fps | 95.2% |
| Alliant Reloder-25 | <<locked>> | 96% | 35,128 psi | 68% | 2621 fps | 95.1% |
| Alliant Reloder-26 | 45.3 gr | 88% | 33,620 psi | 65% | 2631 fps | 95.6% |
| Bofors RP3 | <<locked>> | 80% | 42,801 psi | 83% | 2690 fps | 99.8% |
| Bofors RP7 | <<locked>> | 84% | 43,352 psi | 84% | 2667 fps | 95.7% |
| Hodgdon H380 | <<locked>> | 80% | 43,627 psi | 85% | 2703 fps | 98.4% |
| Hodgdon H414 | <<locked>> | 84% | 40,785 psi | 79% | 2694 fps | 95.6% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 30,821 psi | 60% | 2441 fps | 97% |
| Hodgdon Superformance | <<locked>> | 86% | 43,018 psi | 84% | 2769 fps | 95.8% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,861 psi | 52% | 1594 fps | 100% |
| IMR 4350 | <<locked>> | 86% | 41,176 psi | 80% | 2644 fps | 95% |
| IMR 4451 Enduron | <<locked>> | 80% | 39,697 psi | 77% | 2592 fps | 95.1% |
| IMR 4831 | <<locked>> | 80% | 32,532 psi | 63% | 2490 fps | 95.9% |
| Lovex S065 | <<locked>> | 80% | 37,144 psi | 72% | 2539 fps | 95.9% |
| Lovex S070 | <<locked>> | 84% | 40,118 psi | 78% | 2625 fps | 95.6% |
| Lovex S071 | <<locked>> | 98% | 37,637 psi | 73% | 2608 fps | 95.8% |
| Norma MRP | 47 gr | 94% | 41,582 psi | 81% | 2789 fps | 95.7% |
| Norma URP | <<locked>> | 80% | 33,620 psi | 65% | 2530 fps | 96% |
| Ramshot Hunter | <<locked>> | 84% | 37,434 psi | 73% | 2628 fps | 95.5% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,441 psi | 53% | 1637 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 39,726 psi | 77% | 2733 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 33,315 psi | 65% | 2546 fps | 95.7% |
| ReloadSwiss RS 70 | <<locked>> | 82% | 34,998 psi | 68% | 2605 fps | 95.6% |
| Rottweil R 903 | <<locked>> | 80% | 40,379 psi | 78% | 2638 fps | 99.5% |
| Rottweil R 907 | <<locked>> | 84% | 43,352 psi | 84% | 2667 fps | 95.7% |
| Shooters World Long Rifle | <<locked>> | 80% | 37,144 psi | 72% | 2539 fps | 95.9% |
| Shooters World SW4350 | <<locked>> | 84% | 40,118 psi | 78% | 2625 fps | 95.6% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 41,495 psi | 81% | 2690 fps | 99.2% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 42,090 psi | 82% | 2562 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 82% | 38,885 psi | 76% | 2539 fps | 95% |
| Somchem S355 | <<locked>> | 80% | 40,973 psi | 80% | 2638 fps | 99.4% |
| Somchem S365 | <<locked>> | 80% | 30,182 psi | 59% | 2484 fps | 98.2% |
| Somchem S385 | <<locked>> | 92% | 42,090 psi | 82% | 2697 fps | 95.3% |
| Vihtavuori N150 | <<locked>> | 80% | 39,030 psi | 76% | 2572 fps | 99.8% |
| Vihtavuori N160 | <<locked>> | 80% | 34,969 psi | 68% | 2530 fps | 96.5% |
| Vihtavuori N550 | <<locked>> | 80% | 34,635 psi | 67% | 2533 fps | 96.1% |
| Vihtavuori N555 | 39.5 gr | 84% | 29,994 psi | 58% | 2477 fps | 95.4% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 34,374 psi | 67% | 2503 fps | 98.4% |
| Winchester 760 | <<locked>> | 84% | 40,785 psi | 79% | 2694 fps | 95.6% |
| Winchester StaBALL HD | <<locked>> | 88% | 27,528 psi | 53% | 2477 fps | 95.8% |
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 46 powders for .257 Roberts loaded with the .257 | 117gr | Sellier & Bellot SPFN. Alliant Reloder-26 delivers the highest muzzle velocity at 2,894 fps; across all powders the maximum-charge window runs from 1,785 fps to 2,894 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 46 of the 46 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (355 MPa), the top charges use 70–90 %, 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. Alliant Reloder-23, Alliant Reloder-25, 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. Norma MRP, Alliant Reloder-26, Vihtavuori N555 rank at the top here: for .257 Roberts 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.