Load Specifications
Load data in caliber .257 Roberts with .257 | 100gr | Barnes X BT bullet and 42 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-17, 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.
A valid access license is required to use the Personalized Load Calculator.
You can find more information in our FAQ: How can I use the Personalized Load Calculator?
Max Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 4064 | <<locked>> | 82% | 45,150 psi | 88% | 2877 fps | 100% |
| Accurate 4350 | <<locked>> | 92% | 46,325 psi | 90% | 2972 fps | 97.8% |
| ADI AR 2208 | <<locked>> | 84% | 44,976 psi | 87% | 2871 fps | 98% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 45,556 psi | 88% | 3015 fps | 98% |
| Alliant Reloder- TS 15.5 | <<locked>> | 84% | 45,165 psi | 88% | 2900 fps | 99.2% |
| Alliant Reloder-15 | <<locked>> | 82% | 45,382 psi | 88% | 2913 fps | 98.2% |
| Alliant Reloder-16 | <<locked>> | 92% | 44,440 psi | 86% | 2963 fps | 97.6% |
| Alliant Reloder-17 | <<locked>> | 88% | 44,759 psi | 87% | 2999 fps | 99.1% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 41,524 psi | 81% | 2920 fps | 98.4% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 46,311 psi | 90% | 3087 fps | 97.5% |
| Bofors RP3 | <<locked>> | 84% | 45,643 psi | 89% | 2917 fps | 99.3% |
| Hodgdon H380 | <<locked>> | 84% | 46,122 psi | 90% | 2913 fps | 97.2% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 44,150 psi | 86% | 2907 fps | 98.8% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 46,180 psi | 90% | 2963 fps | 99.4% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,027 psi | 70% | 1909 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 44,585 psi | 87% | 2854 fps | 98.1% |
| IMR 4831 | <<locked>> | 92% | 44,005 psi | 85% | 2910 fps | 97.4% |
| IMR 4895 | <<locked>> | 82% | 46,499 psi | 90% | 2946 fps | 98.9% |
| Lovex S062 | <<locked>> | 82% | 44,991 psi | 87% | 2864 fps | 99.4% |
| Lovex S065 | <<locked>> | 88% | 44,367 psi | 86% | 2848 fps | 95.8% |
| Norma 203B | <<locked>> | 82% | 44,802 psi | 87% | 2900 fps | 98.5% |
| Norma URP | <<locked>> | 92% | 45,382 psi | 88% | 2956 fps | 97.5% |
| Ramshot Big Game | <<locked>> | 82% | 44,324 psi | 86% | 2913 fps | 98.3% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,608 psi | 71% | 1952 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 44,469 psi | 86% | 3005 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 45,440 psi | 88% | 2982 fps | 97.3% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 44,976 psi | 87% | 2986 fps | 96.5% |
| Rottweil R 903 | <<locked>> | 86% | 45,469 psi | 88% | 2907 fps | 99.1% |
| Shooters World Long Rifle | <<locked>> | 88% | 44,367 psi | 86% | 2848 fps | 95.8% |
| Shooters World Precision | <<locked>> | 82% | 44,991 psi | 87% | 2864 fps | 99.4% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 46,282 psi | 90% | 2959 fps | 98.7% |
| SNPE Vectan Tubal 5000 | <<locked>> | 84% | 44,527 psi | 86% | 2779 fps | 100% |
| Somchem S355 | <<locked>> | 86% | 46,050 psi | 89% | 2910 fps | 99.1% |
| Somchem S365 | <<locked>> | 96% | 46,485 psi | 90% | 3022 fps | 99.9% |
| Vihtavuori N135 | <<locked>> | 82% | 46,224 psi | 90% | 2858 fps | 100% |
| Vihtavuori N150 | <<locked>> | 86% | 43,888 psi | 85% | 2835 fps | 99.5% |
| Vihtavuori N160 | <<locked>> | 90% | 44,396 psi | 86% | 2897 fps | 97.2% |
| Vihtavuori N540 | <<locked>> | 82% | 45,092 psi | 88% | 2854 fps | 100% |
| Vihtavuori N550 | <<locked>> | 90% | 43,874 psi | 85% | 2900 fps | 96.9% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 45,585 psi | 89% | 3009 fps | 98.3% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 44,309 psi | 86% | 2871 fps | 99% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 37,536 psi | 73% | 2920 fps | 98.1% |
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 4064 | <<locked>> | 80% | 42,627 psi | 83% | 2828 fps | 100% |
| Accurate 4350 | <<locked>> | 86% | 38,159 psi | 74% | 2799 fps | 95.6% |
| ADI AR 2208 | <<locked>> | 80% | 40,030 psi | 78% | 2762 fps | 96.8% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 42,699 psi | 83% | 2949 fps | 97.3% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 40,132 psi | 78% | 2795 fps | 98.3% |
| Alliant Reloder-15 | <<locked>> | 80% | 42,801 psi | 83% | 2858 fps | 97.6% |
| Alliant Reloder-16 | 38.9 gr | 86% | 37,347 psi | 73% | 2792 fps | 95.3% |
| Alliant Reloder-17 | 39 gr | 80% | 34,795 psi | 68% | 2753 fps | 96.2% |
| Alliant Reloder-23 | <<locked>> | 92% | 32,880 psi | 64% | 2694 fps | 95.2% |
| Alliant Reloder-26 | <<locked>> | 96% | 40,611 psi | 79% | 2956 fps | 95.7% |
| Bofors RP3 | <<locked>> | 80% | 40,234 psi | 78% | 2805 fps | 98.4% |
| Hodgdon H380 | <<locked>> | 80% | 40,727 psi | 79% | 2799 fps | 95.7% |
| Hodgdon Hybrid 100V | <<locked>> | 84% | 32,822 psi | 64% | 2638 fps | 95.5% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 43,163 psi | 84% | 2904 fps | 99% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,832 psi | 52% | 1703 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 42,047 psi | 82% | 2799 fps | 97.5% |
| IMR 4831 | <<locked>> | 86% | 36,535 psi | 71% | 2743 fps | 95.1% |
| IMR 4895 | <<locked>> | 80% | 43,845 psi | 85% | 2890 fps | 98.4% |
| Lovex S062 | <<locked>> | 80% | 42,467 psi | 82% | 2812 fps | 99% |
| Lovex S065 | <<locked>> | 86% | 41,916 psi | 81% | 2795 fps | 95.1% |
| Norma 203B | <<locked>> | 80% | 42,279 psi | 82% | 2848 fps | 98% |
| Norma URP | <<locked>> | 86% | 37,695 psi | 73% | 2785 fps | 95.2% |
| Ramshot Big Game | <<locked>> | 80% | 41,481 psi | 81% | 2851 fps | 97.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,412 psi | 53% | 1749 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 36,825 psi | 72% | 2825 fps | 99.1% |
| ReloadSwiss RS 62 | <<locked>> | 88% | 40,016 psi | 78% | 2867 fps | 95.8% |
| ReloadSwiss RS 70 | 44.6 gr | 90% | 42,409 psi | 82% | 2930 fps | 95.7% |
| Rottweil R 903 | <<locked>> | 80% | 38,029 psi | 74% | 2746 fps | 97.6% |
| Shooters World Long Rifle | <<locked>> | 86% | 41,916 psi | 81% | 2795 fps | 95.1% |
| Shooters World Precision | <<locked>> | 80% | 42,467 psi | 82% | 2812 fps | 99% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 38,232 psi | 74% | 2785 fps | 96.9% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 39,755 psi | 77% | 2687 fps | 100% |
| Somchem S355 | <<locked>> | 80% | 38,595 psi | 75% | 2749 fps | 97.6% |
| Somchem S365 | <<locked>> | 80% | 28,645 psi | 56% | 2572 fps | 95.1% |
| Vihtavuori N135 | <<locked>> | 80% | 43,729 psi | 85% | 2815 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 36,666 psi | 71% | 2680 fps | 98.3% |
| Vihtavuori N160 | <<locked>> | 86% | 39,349 psi | 76% | 2789 fps | 95.7% |
| Vihtavuori N540 | <<locked>> | 80% | 42,583 psi | 83% | 2805 fps | 99.9% |
| Vihtavuori N550 | <<locked>> | 86% | 38,812 psi | 75% | 2789 fps | 95.3% |
| Vihtavuori N555 | <<locked>> | 92% | 35,534 psi | 69% | 2782 fps | 95.4% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 32,445 psi | 63% | 2589 fps | 95.5% |
| Winchester StaBALL HD | <<locked>> | 96% | 33,344 psi | 65% | 2785 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 42 powders for .257 Roberts loaded with the .257 | 100gr | Barnes X BT. Alliant Reloder-26 delivers the highest muzzle velocity at 3,087 fps; across all powders the maximum-charge window runs from 1,909 fps to 3,087 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 42 of the 42 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 100.0 gr projectile in 0.257" calls for a 1:10.0 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-17, ReloadSwiss RS 70, Alliant Reloder-16 rank at the top here: for .257 Roberts with the .257 | 100gr | Barnes X BT 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.