Load Specifications
Load data in caliber .257 Roberts with .257 | 120gr | Winchester Soft-Point bullet and 45 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 ReloadSwiss RS 70.
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% | 45,730 psi | 89% | 2736 fps | 98.1% |
| Accurate 4350 | <<locked>> | 88% | 44,628 psi | 87% | 2736 fps | 99.1% |
| ADI AR 2208 | <<locked>> | 82% | 46,035 psi | 89% | 2687 fps | 99.5% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 46,282 psi | 90% | 2713 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 90% | 46,238 psi | 90% | 2802 fps | 99.6% |
| Alliant Reloder-17 | <<locked>> | 86% | 46,514 psi | 90% | 2822 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 45,977 psi | 89% | 2815 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 40,393 psi | 78% | 2723 fps | 97.6% |
| Alliant Reloder-26 | <<locked>> | 96% | 45,426 psi | 88% | 2874 fps | 99.3% |
| Bofors RP3 | <<locked>> | 82% | 46,311 psi | 90% | 2720 fps | 100% |
| Bofors RP7 | <<locked>> | 86% | 46,398 psi | 90% | 2694 fps | 96.7% |
| Hodgdon H414 | <<locked>> | 86% | 44,179 psi | 86% | 2730 fps | 96.9% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 45,977 psi | 89% | 2733 fps | 100% |
| Hodgdon Superformance | <<locked>> | 86% | 43,337 psi | 84% | 2743 fps | 96.2% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,158 psi | 70% | 1762 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 44,164 psi | 86% | 2671 fps | 96.2% |
| IMR 4451 Enduron | <<locked>> | 84% | 45,324 psi | 88% | 2674 fps | 96.9% |
| IMR 4831 | <<locked>> | 90% | 45,571 psi | 89% | 2736 fps | 99.3% |
| Lovex S065 | <<locked>> | 86% | 45,136 psi | 88% | 2674 fps | 98.2% |
| Lovex S070 | <<locked>> | 88% | 45,977 psi | 89% | 2710 fps | 97.4% |
| Lovex S071ᴾ | <<locked>> | 100% | 40,727 psi | 79% | 2641 fps | 97% |
| Norma MRP | <<locked>> | 96% | 44,933 psi | 87% | 2828 fps | 97% |
| Norma URP | <<locked>> | 88% | 44,324 psi | 86% | 2730 fps | 99% |
| Ramshot Hunter | <<locked>> | 90% | 46,079 psi | 89% | 2776 fps | 98.1% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,738 psi | 71% | 1804 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 46,151 psi | 90% | 2822 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 44,338 psi | 86% | 2756 fps | 98.9% |
| ReloadSwiss RS 70 | <<locked>> | 88% | 43,642 psi | 85% | 2776 fps | 98.6% |
| Rottweil R 903 | <<locked>> | 84% | 46,514 psi | 90% | 2717 fps | 100% |
| Rottweil R 907 | <<locked>> | 86% | 46,398 psi | 90% | 2694 fps | 96.7% |
| Shooters World Long Rifle | <<locked>> | 86% | 45,136 psi | 88% | 2674 fps | 98.2% |
| Shooters World SW4350 | <<locked>> | 88% | 45,977 psi | 89% | 2710 fps | 97.4% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 44,860 psi | 87% | 2720 fps | 99.7% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 45,411 psi | 88% | 2582 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 86% | 44,585 psi | 87% | 2621 fps | 96.9% |
| Somchem S355 | <<locked>> | 82% | 44,193 psi | 86% | 2667 fps | 99.8% |
| Somchem S365 | <<locked>> | 92% | 45,832 psi | 89% | 2789 fps | 100% |
| Somchem S385 | <<locked>> | 94% | 45,339 psi | 88% | 2726 fps | 96.5% |
| Vihtavuori N150 | <<locked>> | 84% | 44,860 psi | 87% | 2648 fps | 100% |
| Vihtavuori N160 | <<locked>> | 88% | 46,006 psi | 89% | 2723 fps | 99.2% |
| Vihtavuori N550 | <<locked>> | 88% | 45,556 psi | 88% | 2733 fps | 99% |
| Vihtavuori N555 | <<locked>> | 96% | 45,281 psi | 88% | 2789 fps | 99.6% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 45,498 psi | 88% | 2700 fps | 100% |
| Winchester 760 | <<locked>> | 86% | 44,179 psi | 86% | 2730 fps | 96.9% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 41,466 psi | 81% | 2854 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>> | 90% | 34,795 psi | 68% | 2513 fps | 95% |
| Accurate 4350 | <<locked>> | 80% | 34,084 psi | 66% | 2513 fps | 96.6% |
| ADI AR 2208 | <<locked>> | 80% | 43,033 psi | 84% | 2631 fps | 99.2% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 43,236 psi | 84% | 2657 fps | 99.9% |
| Alliant Reloder-16 | <<locked>> | 80% | 33,750 psi | 66% | 2523 fps | 96.7% |
| Alliant Reloder-17 | <<locked>> | 80% | 37,768 psi | 73% | 2644 fps | 99.3% |
| Alliant Reloder-23 | <<locked>> | 84% | 27,833 psi | 54% | 2382 fps | 95.7% |
| Alliant Reloder-25 | <<locked>> | 96% | 35,607 psi | 69% | 2605 fps | 95.7% |
| Alliant Reloder-26 | 43.9 gr | 86% | 31,865 psi | 62% | 2552 fps | 95% |
| Bofors RP3 | <<locked>> | 80% | 43,482 psi | 84% | 2667 fps | 99.9% |
| Bofors RP7 | <<locked>> | 82% | 41,104 psi | 80% | 2589 fps | 95.3% |
| Hodgdon H414 | <<locked>> | 82% | 38,522 psi | 75% | 2612 fps | 95.1% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 31,096 psi | 60% | 2418 fps | 97.4% |
| Hodgdon Superformance | <<locked>> | 84% | 40,509 psi | 79% | 2684 fps | 95.3% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,977 psi | 52% | 1575 fps | 100% |
| IMR 4350 | <<locked>> | 86% | 41,597 psi | 81% | 2621 fps | 95.5% |
| IMR 4451 Enduron | <<locked>> | 80% | 39,987 psi | 78% | 2566 fps | 95.4% |
| IMR 4831 | <<locked>> | 80% | 32,837 psi | 64% | 2464 fps | 96.2% |
| Lovex S065 | <<locked>> | 80% | 37,434 psi | 73% | 2516 fps | 96.3% |
| Lovex S070 | <<locked>> | 82% | 38,101 psi | 74% | 2546 fps | 95.2% |
| Lovex S071 | <<locked>> | 96% | 35,810 psi | 70% | 2536 fps | 95.4% |
| Norma MRP | 45.5 gr | 92% | 39,218 psi | 76% | 2703 fps | 95.1% |
| Norma URP | <<locked>> | 80% | 33,968 psi | 66% | 2507 fps | 96.4% |
| Ramshot Hunter | <<locked>> | 82% | 35,404 psi | 69% | 2549 fps | 95% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,296 psi | 53% | 1611 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 40,147 psi | 78% | 2707 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 33,707 psi | 65% | 2526 fps | 96.1% |
| ReloadSwiss RS 70 | 40.4 gr | 80% | 33,098 psi | 64% | 2523 fps | 95% |
| Rottweil R 903 | <<locked>> | 80% | 40,756 psi | 79% | 2612 fps | 99.6% |
| Rottweil R 907 | <<locked>> | 82% | 41,104 psi | 80% | 2589 fps | 95.3% |
| Shooters World Long Rifle | <<locked>> | 80% | 37,434 psi | 73% | 2516 fps | 96.3% |
| Shooters World SW4350 | <<locked>> | 82% | 38,101 psi | 74% | 2546 fps | 95.2% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 41,887 psi | 81% | 2664 fps | 99.4% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 42,641 psi | 83% | 2536 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 82% | 39,204 psi | 76% | 2513 fps | 95.4% |
| Somchem S355 | <<locked>> | 80% | 41,292 psi | 80% | 2612 fps | 99.6% |
| Somchem S365 | <<locked>> | 80% | 30,516 psi | 59% | 2461 fps | 98.5% |
| Somchem S385 | <<locked>> | 92% | 42,351 psi | 82% | 2671 fps | 95.7% |
| Vihtavuori N150 | <<locked>> | 80% | 39,320 psi | 76% | 2546 fps | 99.9% |
| Vihtavuori N160 | <<locked>> | 80% | 35,534 psi | 69% | 2513 fps | 96.9% |
| Vihtavuori N550 | <<locked>> | 80% | 34,983 psi | 68% | 2510 fps | 96.5% |
| Vihtavuori N555 | <<locked>> | 84% | 30,356 psi | 59% | 2457 fps | 95.8% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 34,708 psi | 67% | 2480 fps | 98.7% |
| Winchester 760 | <<locked>> | 82% | 38,783 psi | 75% | 2618 fps | 95.2% |
| Winchester StaBALL HD | <<locked>> | 86% | 26,121 psi | 51% | 2398 fps | 95% |
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 45 powders for .257 Roberts loaded with the .257 | 120gr | Winchester Soft-Point. Alliant Reloder-26 delivers the highest muzzle velocity at 2,874 fps; across all powders the maximum-charge window runs from 1,762 fps to 2,874 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 45 of the 45 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 120.0 gr projectile in 0.257" calls for a 1:12.5 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, ReloadSwiss RS 70 rank at the top here: for .257 Roberts with the .257 | 120gr | Winchester Soft-Point 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.