Load Specifications
Load data in caliber .257 Roberts with .257 | 120gr | Speer Deep Curl Soft Point bullet and 50 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-26, Norma MRP and Alliant Reloder-16.
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 2700 | <<locked>> | 84% | 46,108 psi | 90% | 2635 fps | 96.3% |
| Accurate 3100 | <<locked>> | 98% | 44,251 psi | 86% | 2703 fps | 97.7% |
| Accurate 4350 | <<locked>> | 90% | 46,543 psi | 90% | 2762 fps | 99.3% |
| ADI AR 2208 | <<locked>> | 82% | 45,005 psi | 87% | 2661 fps | 99.4% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 45,150 psi | 88% | 2684 fps | 99.9% |
| Alliant Reloder-16 | <<locked>> | 90% | 44,933 psi | 87% | 2769 fps | 99.4% |
| Alliant Reloder-17 | <<locked>> | 86% | 45,194 psi | 88% | 2792 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 44,556 psi | 87% | 2782 fps | 99.9% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 39,262 psi | 76% | 2690 fps | 97% |
| Alliant Reloder-26 | <<locked>> | 96% | 43,743 psi | 85% | 2835 fps | 98.9% |
| Bofors RP3 | <<locked>> | 82% | 45,179 psi | 88% | 2694 fps | 100% |
| Bofors RP7 | <<locked>> | 86% | 45,484 psi | 88% | 2667 fps | 96.3% |
| Hodgdon H380 | <<locked>> | 82% | 45,745 psi | 89% | 2700 fps | 98.8% |
| Hodgdon H414 | <<locked>> | 88% | 46,064 psi | 89% | 2759 fps | 97.2% |
| Hodgdon H4350 | <<locked>> | 86% | 46,412 psi | 90% | 2720 fps | 95.8% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 44,976 psi | 87% | 2710 fps | 99.9% |
| Hodgdon Superformance | <<locked>> | 88% | 45,339 psi | 88% | 2776 fps | 96.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,940 psi | 70% | 1749 fps | 100% |
| IMR 4350 | <<locked>> | 90% | 46,021 psi | 89% | 2700 fps | 96.5% |
| IMR 4451 Enduron | <<locked>> | 84% | 44,411 psi | 86% | 2651 fps | 96.6% |
| IMR 4831 | <<locked>> | 90% | 44,295 psi | 86% | 2707 fps | 99.1% |
| Lovex S065 | <<locked>> | 86% | 44,164 psi | 86% | 2648 fps | 97.9% |
| Lovex S070 | <<locked>> | 88% | 44,730 psi | 87% | 2680 fps | 97% |
| Lovex S071ᴾ | <<locked>> | 100% | 39,305 psi | 76% | 2608 fps | 96.4% |
| Norma MRP | <<locked>> | 96% | 43,642 psi | 85% | 2792 fps | 96.4% |
| Norma URP | <<locked>> | 90% | 46,195 psi | 90% | 2756 fps | 99.2% |
| Ramshot Hunter | <<locked>> | 90% | 44,918 psi | 87% | 2749 fps | 97.8% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,535 psi | 71% | 1791 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 45,934 psi | 89% | 2684 fps | 97.6% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 44,817 psi | 87% | 2792 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 90% | 46,282 psi | 90% | 2782 fps | 99.1% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 45,310 psi | 88% | 2802 fps | 98.8% |
| Rottweil R 903 | <<locked>> | 84% | 45,411 psi | 88% | 2690 fps | 99.9% |
| Rottweil R 907 | <<locked>> | 86% | 45,484 psi | 88% | 2667 fps | 96.3% |
| Shooters World Long Rifle | <<locked>> | 86% | 44,164 psi | 86% | 2648 fps | 97.9% |
| Shooters World SW4350 | <<locked>> | 88% | 44,730 psi | 87% | 2680 fps | 97% |
| SNPE Vectan SP 11 | <<locked>> | 82% | 43,540 psi | 85% | 2690 fps | 99.5% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 44,309 psi | 86% | 2559 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 88% | 46,557 psi | 90% | 2648 fps | 97.2% |
| Somchem S355 | <<locked>> | 84% | 45,890 psi | 89% | 2694 fps | 99.9% |
| Somchem S365 | <<locked>> | 92% | 44,440 psi | 86% | 2759 fps | 100% |
| Somchem S385 | <<locked>> | 94% | 43,888 psi | 85% | 2694 fps | 95.9% |
| Vihtavuori N150 | <<locked>> | 84% | 43,845 psi | 85% | 2625 fps | 100% |
| Vihtavuori N160 | <<locked>> | 88% | 45,020 psi | 87% | 2700 fps | 99% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 46,340 psi | 90% | 2726 fps | 96.1% |
| Vihtavuori N550 | <<locked>> | 88% | 44,367 psi | 86% | 2703 fps | 98.7% |
| Vihtavuori N555 | <<locked>> | 98% | 46,572 psi | 90% | 2805 fps | 99.7% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 44,469 psi | 86% | 2674 fps | 99.9% |
| Winchester 760 | <<locked>> | 88% | 46,064 psi | 89% | 2759 fps | 97.2% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 40,306 psi | 78% | 2822 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 2700 | <<locked>> | 82% | 43,395 psi | 84% | 2582 fps | 95.5% |
| Accurate 3100 | <<locked>> | 92% | 35,984 psi | 70% | 2536 fps | 95.3% |
| Accurate 4350 | <<locked>> | 80% | 33,054 psi | 64% | 2480 fps | 96.1% |
| ADI AR 2208 | <<locked>> | 80% | 42,308 psi | 82% | 2608 fps | 99% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 42,424 psi | 82% | 2635 fps | 99.8% |
| Alliant Reloder-16 | 36.1 gr | 80% | 32,837 psi | 64% | 2490 fps | 96.1% |
| Alliant Reloder-17 | <<locked>> | 80% | 36,854 psi | 72% | 2618 fps | 99% |
| Alliant Reloder-23 | <<locked>> | 84% | 27,108 psi | 53% | 2352 fps | 95% |
| Alliant Reloder-25 | <<locked>> | 96% | 34,751 psi | 67% | 2575 fps | 95% |
| Alliant Reloder-26 | 43.8 gr | 88% | 32,953 psi | 64% | 2579 fps | 95.4% |
| Bofors RP3 | <<locked>> | 80% | 42,380 psi | 82% | 2641 fps | 99.8% |
| Bofors RP7 | <<locked>> | 84% | 42,743 psi | 83% | 2612 fps | 95.6% |
| Hodgdon H380 | <<locked>> | 80% | 42,946 psi | 83% | 2648 fps | 98.3% |
| Hodgdon H414 | <<locked>> | 84% | 40,335 psi | 78% | 2644 fps | 95.6% |
| Hodgdon H4350 | <<locked>> | 84% | 43,656 psi | 85% | 2667 fps | 95% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 30,414 psi | 59% | 2395 fps | 97% |
| Hodgdon Superformance | <<locked>> | 86% | 42,322 psi | 82% | 2717 fps | 95.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,876 psi | 52% | 1565 fps | 100% |
| IMR 4350 | <<locked>> | 88% | 43,294 psi | 84% | 2648 fps | 95.8% |
| IMR 4451 Enduron | <<locked>> | 82% | 41,800 psi | 81% | 2595 fps | 95.8% |
| IMR 4831 | <<locked>> | 80% | 31,879 psi | 62% | 2438 fps | 95.7% |
| Lovex S065 | <<locked>> | 80% | 36,753 psi | 71% | 2493 fps | 95.9% |
| Lovex S070 | <<locked>> | 84% | 39,552 psi | 77% | 2575 fps | 95.6% |
| Lovex S071 | <<locked>> | 98% | 37,072 psi | 72% | 2559 fps | 95.7% |
| Norma MRP | 45.5 gr | 94% | 40,973 psi | 80% | 2736 fps | 95.6% |
| Norma URP | <<locked>> | 80% | 33,214 psi | 65% | 2480 fps | 96% |
| Ramshot Hunter | <<locked>> | 84% | 36,767 psi | 71% | 2575 fps | 95.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,195 psi | 53% | 1598 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 43,192 psi | 84% | 2631 fps | 97% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 39,189 psi | 76% | 2680 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 32,793 psi | 64% | 2497 fps | 95.6% |
| ReloadSwiss RS 70 | <<locked>> | 82% | 34,650 psi | 67% | 2556 fps | 95.5% |
| Rottweil R 903 | <<locked>> | 80% | 39,943 psi | 78% | 2589 fps | 99.5% |
| Rottweil R 907 | <<locked>> | 84% | 42,743 psi | 83% | 2612 fps | 95.6% |
| Shooters World Long Rifle | <<locked>> | 80% | 36,753 psi | 71% | 2493 fps | 95.9% |
| Shooters World SW4350 | <<locked>> | 84% | 39,552 psi | 77% | 2575 fps | 95.6% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 40,857 psi | 79% | 2638 fps | 99.2% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 41,858 psi | 81% | 2516 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 40,799 psi | 79% | 2539 fps | 95.7% |
| Somchem S355 | <<locked>> | 80% | 40,509 psi | 79% | 2592 fps | 99.4% |
| Somchem S365 | <<locked>> | 80% | 29,805 psi | 58% | 2438 fps | 98.2% |
| Somchem S385 | <<locked>> | 92% | 41,249 psi | 80% | 2641 fps | 95.1% |
| Vihtavuori N150 | <<locked>> | 80% | 38,580 psi | 75% | 2523 fps | 99.8% |
| Vihtavuori N160 | <<locked>> | 80% | 34,577 psi | 67% | 2484 fps | 96.5% |
| Vihtavuori N165 | <<locked>> | 98% | 43,163 psi | 84% | 2664 fps | 95.2% |
| Vihtavuori N550 | <<locked>> | 80% | 34,098 psi | 66% | 2484 fps | 96% |
| Vihtavuori N555 | <<locked>> | 84% | 29,428 psi | 57% | 2431 fps | 95.3% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 33,997 psi | 66% | 2457 fps | 98.4% |
| Winchester 760 | <<locked>> | 84% | 40,335 psi | 78% | 2644 fps | 95.6% |
| Winchester StaBALL HD | <<locked>> | 88% | 27,108 psi | 53% | 2428 fps | 95.6% |
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 50 powders for .257 Roberts loaded with the .257 | 120gr | Speer Deep Curl Soft Point. Alliant Reloder-26 delivers the highest muzzle velocity at 2,835 fps; across all powders the maximum-charge window runs from 1,749 fps to 2,835 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 50 of the 50 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 1:11.0 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. Alliant Reloder-26, Norma MRP, Alliant Reloder-16 rank at the top here: for .257 Roberts with the .257 | 120gr | Speer Deep Curl 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.