Load Specifications
Load data in caliber .257 Roberts with .257 | 117gr | Hornady SST 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-26, ReloadSwiss RS 70 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 3100ᴾ | <<locked>> | 100% | 46,296 psi | 90% | 2769 fps | 97.8% |
| Accurate 4064 | <<locked>> | 82% | 46,093 psi | 90% | 2707 fps | 100% |
| Accurate 4350 | <<locked>> | 90% | 45,672 psi | 89% | 2782 fps | 99% |
| ADI AR 2208 | <<locked>> | 82% | 44,150 psi | 86% | 2677 fps | 99.1% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 44,208 psi | 86% | 2700 fps | 99.8% |
| Alliant Reloder-16 | <<locked>> | 90% | 44,237 psi | 86% | 2789 fps | 99.1% |
| Alliant Reloder-17 | <<locked>> | 86% | 44,425 psi | 86% | 2812 fps | 99.9% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 43,743 psi | 85% | 2799 fps | 99.8% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 38,305 psi | 74% | 2694 fps | 96.2% |
| Alliant Reloder-26 | <<locked>> | 98% | 46,064 psi | 89% | 2913 fps | 99.1% |
| Bofors RP3 | <<locked>> | 82% | 44,512 psi | 86% | 2713 fps | 99.9% |
| Bofors RP7 | <<locked>> | 86% | 44,831 psi | 87% | 2684 fps | 95.8% |
| Hodgdon H380 | <<locked>> | 82% | 45,092 psi | 88% | 2720 fps | 98.5% |
| Hodgdon H414 | <<locked>> | 88% | 44,976 psi | 87% | 2769 fps | 96.6% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 43,888 psi | 85% | 2723 fps | 99.7% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,810 psi | 70% | 1768 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 46,398 psi | 90% | 2710 fps | 99.5% |
| IMR 4350 | <<locked>> | 90% | 45,034 psi | 87% | 2713 fps | 96% |
| IMR 4451 Enduron | <<locked>> | 86% | 46,296 psi | 90% | 2713 fps | 96.7% |
| IMR 4831 | <<locked>> | 92% | 46,398 psi | 90% | 2779 fps | 99.2% |
| Lovex S062 | <<locked>> | 82% | 46,528 psi | 90% | 2713 fps | 100% |
| Lovex S065 | <<locked>> | 88% | 45,963 psi | 89% | 2713 fps | 98% |
| Lovex S070 | <<locked>> | 88% | 44,092 psi | 86% | 2697 fps | 96.6% |
| Norma MRP | <<locked>> | 98% | 45,977 psi | 89% | 2871 fps | 96.8% |
| Norma URP | <<locked>> | 90% | 45,078 psi | 88% | 2769 fps | 98.9% |
| Ramshot Hunter | <<locked>> | 90% | 43,816 psi | 85% | 2756 fps | 97.2% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,376 psi | 71% | 1811 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 45,281 psi | 88% | 2700 fps | 97.2% |
| ReloadSwiss RS 60 | <<locked>> | 84% | 44,077 psi | 86% | 2812 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 90% | 45,397 psi | 88% | 2802 fps | 98.8% |
| ReloadSwiss RS 70 | <<locked>> | 90% | 44,556 psi | 87% | 2815 fps | 98.4% |
| Rottweil R 903 | <<locked>> | 84% | 44,701 psi | 87% | 2713 fps | 99.8% |
| Rottweil R 907 | <<locked>> | 86% | 44,831 psi | 87% | 2684 fps | 95.8% |
| Shooters World Long Rifle | <<locked>> | 88% | 45,963 psi | 89% | 2713 fps | 98% |
| Shooters World Precision | <<locked>> | 82% | 46,528 psi | 90% | 2713 fps | 100% |
| Shooters World SW4350 | <<locked>> | 88% | 44,092 psi | 86% | 2697 fps | 96.6% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 45,585 psi | 89% | 2759 fps | 99.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 82% | 43,772 psi | 85% | 2582 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 88% | 45,600 psi | 89% | 2661 fps | 96.7% |
| Somchem S355 | <<locked>> | 84% | 44,933 psi | 87% | 2707 fps | 99.8% |
| Somchem S365 | <<locked>> | 94% | 46,557 psi | 90% | 2831 fps | 100% |
| Somchem S385 | <<locked>> | 96% | 45,948 psi | 89% | 2762 fps | 96.2% |
| Vihtavuori N150 | <<locked>> | 86% | 46,021 psi | 89% | 2694 fps | 100% |
| Vihtavuori N160 | <<locked>> | 88% | 43,932 psi | 85% | 2713 fps | 98.6% |
| Vihtavuori N550 | <<locked>> | 90% | 46,369 psi | 90% | 2772 fps | 98.9% |
| Vihtavuori N555 | <<locked>> | 98% | 45,629 psi | 89% | 2822 fps | 99.4% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 46,543 psi | 90% | 2743 fps | 100% |
| Winchester 760 | <<locked>> | 88% | 44,976 psi | 87% | 2769 fps | 96.6% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 39,262 psi | 76% | 2825 fps | 99.9% |
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>> | 94% | 37,666 psi | 73% | 2602 fps | 95.5% |
| Accurate 4064 | <<locked>> | 80% | 43,308 psi | 84% | 2657 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 32,184 psi | 63% | 2490 fps | 95.4% |
| ADI AR 2208 | <<locked>> | 80% | 41,452 psi | 81% | 2621 fps | 98.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 41,539 psi | 81% | 2648 fps | 99.6% |
| Alliant Reloder-16 | 36.2 gr | 80% | 32,372 psi | 63% | 2507 fps | 95.6% |
| Alliant Reloder-17 | <<locked>> | 80% | 35,998 psi | 70% | 2628 fps | 98.6% |
| Alliant Reloder-23 | <<locked>> | 86% | 28,152 psi | 55% | 2411 fps | 95.3% |
| Alliant Reloder-25 | <<locked>> | 98% | 36,085 psi | 70% | 2638 fps | 95.3% |
| Alliant Reloder-26 | 44.9 gr | 90% | 34,693 psi | 67% | 2654 fps | 95.8% |
| Bofors RP3 | <<locked>> | 80% | 41,423 psi | 80% | 2654 fps | 99.6% |
| Bofors RP7 | <<locked>> | 84% | 42,192 psi | 82% | 2631 fps | 95.1% |
| Hodgdon H380 | <<locked>> | 80% | 42,047 psi | 82% | 2661 fps | 97.9% |
| Hodgdon H414 | <<locked>> | 86% | 41,945 psi | 81% | 2710 fps | 95.8% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 29,704 psi | 58% | 2402 fps | 96.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,760 psi | 52% | 1581 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 43,569 psi | 85% | 2657 fps | 99.2% |
| IMR 4350 | <<locked>> | 88% | 42,395 psi | 82% | 2657 fps | 95.2% |
| IMR 4451 Enduron | <<locked>> | 82% | 40,988 psi | 80% | 2608 fps | 95.2% |
| IMR 4831 | <<locked>> | 80% | 31,328 psi | 61% | 2451 fps | 95.1% |
| Lovex S062 | <<locked>> | 80% | 43,714 psi | 85% | 2661 fps | 99.9% |
| Lovex S065 | <<locked>> | 80% | 35,984 psi | 70% | 2503 fps | 95.2% |
| Lovex S070 | <<locked>> | 84% | 38,972 psi | 76% | 2589 fps | 95% |
| Norma MRP | <<locked>> | 96% | 42,844 psi | 83% | 2805 fps | 95.8% |
| Norma URP | <<locked>> | 80% | 32,416 psi | 63% | 2490 fps | 95.3% |
| Ramshot Hunter | <<locked>> | 86% | 38,479 psi | 75% | 2644 fps | 95.6% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,340 psi | 53% | 1624 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 42,322 psi | 82% | 2641 fps | 96.5% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 38,290 psi | 74% | 2694 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 82% | 34,316 psi | 67% | 2566 fps | 95.9% |
| ReloadSwiss RS 70 | 41.5 gr | 84% | 36,245 psi | 70% | 2625 fps | 95.8% |
| Rottweil R 903 | <<locked>> | 80% | 39,030 psi | 76% | 2598 fps | 99.2% |
| Rottweil R 907 | <<locked>> | 84% | 42,192 psi | 82% | 2631 fps | 95.1% |
| Shooters World Long Rifle | <<locked>> | 80% | 35,984 psi | 70% | 2503 fps | 95.2% |
| Shooters World Precision | <<locked>> | 80% | 43,714 psi | 85% | 2661 fps | 99.9% |
| Shooters World SW4350 | <<locked>> | 84% | 38,972 psi | 76% | 2589 fps | 95% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 39,943 psi | 78% | 2651 fps | 98.8% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 41,017 psi | 80% | 2533 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 40,248 psi | 78% | 2556 fps | 95.2% |
| Somchem S355 | <<locked>> | 80% | 39,653 psi | 77% | 2605 fps | 99.1% |
| Somchem S365 | <<locked>> | 80% | 29,080 psi | 56% | 2444 fps | 97.6% |
| Somchem S385 | <<locked>> | 94% | 43,105 psi | 84% | 2707 fps | 95.4% |
| Vihtavuori N150 | <<locked>> | 80% | 37,753 psi | 73% | 2536 fps | 99.6% |
| Vihtavuori N160 | <<locked>> | 80% | 33,750 psi | 66% | 2493 fps | 95.8% |
| Vihtavuori N550 | <<locked>> | 80% | 33,257 psi | 65% | 2493 fps | 95.4% |
| Vihtavuori N555 | <<locked>> | 86% | 30,560 psi | 59% | 2490 fps | 95.5% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 33,286 psi | 65% | 2467 fps | 97.9% |
| Winchester 760 | <<locked>> | 86% | 42,235 psi | 82% | 2717 fps | 95.9% |
| Winchester StaBALL HD | <<locked>> | 90% | 28,297 psi | 55% | 2493 fps | 96% |
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 | 117gr | Hornady SST. Alliant Reloder-26 delivers the highest muzzle velocity at 2,913 fps; across all powders the maximum-charge window runs from 1,768 fps to 2,913 fps. Accurate 3100 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 70–90 %, leaving at least 10 % headroom. The 117.0 gr projectile in 0.257" calls for a 1:11.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, Alliant Reloder-23, Alliant Reloder-25 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, ReloadSwiss RS 70, Alliant Reloder-16 rank at the top here: for .257 Roberts with the .257 | 117gr | Hornady SST 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.