Load Specifications
Load data in caliber .257 Roberts with .257 | 100gr | Osprey Virtus bullet and 63 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 60, Alliant Reloder-17 and ReloadSwiss RS 62.
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 2495 | <<locked>> | 84% | 43,714 psi | 85% | 2848 fps | 100% |
| Accurate 4064 | <<locked>> | 86% | 44,034 psi | 86% | 2890 fps | 100% |
| Accurate 4350 | <<locked>> | 96% | 46,470 psi | 90% | 2999 fps | 97.8% |
| ADI AR 2206H | <<locked>> | 82% | 45,150 psi | 88% | 2913 fps | 98.5% |
| ADI AR 2208 | <<locked>> | 88% | 46,456 psi | 90% | 2920 fps | 98.2% |
| Alliant Power Pro 2000-MR | <<locked>> | 84% | 44,338 psi | 86% | 3009 fps | 97.7% |
| Alliant Reloder- TS 15.5 | <<locked>> | 88% | 45,861 psi | 89% | 2940 fps | 99.3% |
| Alliant Reloder-15 | <<locked>> | 86% | 46,528 psi | 90% | 2959 fps | 98.4% |
| Alliant Reloder-16 | <<locked>> | 96% | 45,585 psi | 89% | 3009 fps | 97.9% |
| Alliant Reloder-17 | <<locked>> | 92% | 46,064 psi | 89% | 3045 fps | 99.3% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 36,564 psi | 71% | 2825 fps | 96.9% |
| Baschieri & Pellagri 107 | <<locked>> | 82% | 44,628 psi | 87% | 2917 fps | 97.5% |
| Bofors RP3 | <<locked>> | 88% | 45,716 psi | 89% | 2946 fps | 99.3% |
| Hodgdon BL-C2 | <<locked>> | 82% | 46,282 psi | 90% | 2946 fps | 99.7% |
| Hodgdon H380 | <<locked>> | 86% | 43,845 psi | 85% | 2894 fps | 96.7% |
| Hodgdon H4895 | <<locked>> | 82% | 45,571 psi | 89% | 2927 fps | 99% |
| Hodgdon Hybrid 100V | <<locked>> | 98% | 44,759 psi | 87% | 2940 fps | 98.9% |
| Hodgdon LEVERevolution | <<locked>> | 84% | 44,599 psi | 87% | 2953 fps | 99.2% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,070 psi | 68% | 1900 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 43,932 psi | 85% | 2877 fps | 98.7% |
| IMR 3031 | <<locked>> | 82% | 45,005 psi | 87% | 2927 fps | 100% |
| IMR 4064 | <<locked>> | 86% | 45,832 psi | 89% | 2900 fps | 98.3% |
| IMR 4831 | <<locked>> | 96% | 44,396 psi | 86% | 2943 fps | 97.5% |
| IMR 4895 | <<locked>> | 84% | 44,440 psi | 86% | 2930 fps | 98.5% |
| Lovex D073.6 | <<locked>> | 82% | 44,237 psi | 86% | 2894 fps | 99.9% |
| Lovex S060 | <<locked>> | 82% | 45,426 psi | 88% | 2851 fps | 98.6% |
| Lovex S062 | <<locked>> | 86% | 45,498 psi | 88% | 2900 fps | 99.4% |
| Lovex S065 | <<locked>> | 92% | 44,875 psi | 87% | 2884 fps | 96% |
| Norma 201 | <<locked>> | 82% | 44,135 psi | 86% | 2864 fps | 99.3% |
| Norma 202 | <<locked>> | 82% | 44,498 psi | 86% | 2877 fps | 100% |
| Norma 203B | <<locked>> | 86% | 45,803 psi | 89% | 2946 fps | 98.7% |
| Norma URP | <<locked>> | 96% | 46,267 psi | 90% | 2995 fps | 97.7% |
| Ramshot Big Game | <<locked>> | 86% | 45,890 psi | 89% | 2966 fps | 98.6% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,418 psi | 69% | 1946 fps | 100% |
| ReloadSwiss RS 52 | <<locked>> | 84% | 46,064 psi | 89% | 3015 fps | 98.3% |
| ReloadSwiss RS 60 | <<locked>> | 90% | 46,108 psi | 90% | 3058 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 96% | 46,267 psi | 90% | 3018 fps | 97.5% |
| ReloadSwiss RS 70 | <<locked>> | 94% | 43,511 psi | 85% | 2972 fps | 96.1% |
| Rottweil R 902 | <<locked>> | 84% | 44,788 psi | 87% | 2867 fps | 99.3% |
| Rottweil R 903 | <<locked>> | 90% | 45,948 psi | 89% | 2943 fps | 99.2% |
| Shooters World Long Rifle | <<locked>> | 92% | 44,875 psi | 87% | 2884 fps | 96% |
| Shooters World Match Rifle | <<locked>> | 82% | 44,237 psi | 86% | 2894 fps | 99.9% |
| Shooters World Precision | <<locked>> | 86% | 45,498 psi | 88% | 2900 fps | 99.4% |
| SNPE Vectan SP 11 | <<locked>> | 88% | 44,440 psi | 86% | 2943 fps | 98.4% |
| SNPE Vectan SP 3 | <<locked>> | 82% | 46,195 psi | 90% | 2822 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 82% | 45,730 psi | 89% | 2900 fps | 97% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 43,903 psi | 85% | 2884 fps | 98.3% |
| SNPE Vectan Tubal 3000 | <<locked>> | 82% | 45,905 psi | 89% | 2825 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 88% | 45,948 psi | 89% | 2825 fps | 100% |
| Somchem S335 | <<locked>> | 82% | 45,223 psi | 88% | 2822 fps | 100% |
| Somchem S341 | <<locked>> | 82% | 45,440 psi | 88% | 2900 fps | 98.5% |
| Somchem S355 | <<locked>> | 90% | 46,543 psi | 90% | 2946 fps | 99.1% |
| Somchem S365 | <<locked>> | 98% | 44,251 psi | 86% | 2999 fps | 99.7% |
| Vihtavuori N133 | <<locked>> | 82% | 46,195 psi | 90% | 2822 fps | 100% |
| Vihtavuori N135 | <<locked>> | 84% | 43,990 psi | 85% | 2848 fps | 100% |
| Vihtavuori N140 | <<locked>> | 84% | 44,947 psi | 87% | 2858 fps | 100% |
| Vihtavuori N150 | <<locked>> | 90% | 44,831 psi | 87% | 2877 fps | 99.6% |
| Vihtavuori N160 | <<locked>> | 94% | 45,600 psi | 89% | 2943 fps | 97.4% |
| Vihtavuori N540 | <<locked>> | 86% | 46,267 psi | 90% | 2897 fps | 100% |
| Vihtavuori N550 | <<locked>> | 94% | 44,643 psi | 87% | 2940 fps | 97.1% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 39,537 psi | 77% | 2904 fps | 96.8% |
| Winchester 6.5 StaBALL | <<locked>> | 94% | 46,035 psi | 89% | 2923 fps | 99.3% |
| Winchester StaBALL Match | <<locked>> | 84% | 46,485 psi | 90% | 2946 fps | 99.2% |
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 2495 | <<locked>> | 80% | 38,159 psi | 74% | 2740 fps | 100% |
| Accurate 4064 | <<locked>> | 80% | 36,114 psi | 70% | 2723 fps | 99.6% |
| Accurate 4350 | <<locked>> | 90% | 37,391 psi | 73% | 2808 fps | 95.3% |
| ADI AR 2206H | <<locked>> | 80% | 42,380 psi | 82% | 2858 fps | 98% |
| ADI AR 2208 | <<locked>> | 80% | 35,998 psi | 70% | 2690 fps | 95.4% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 38,406 psi | 75% | 2867 fps | 95.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 35,360 psi | 69% | 2710 fps | 97% |
| Alliant Reloder-15 | <<locked>> | 80% | 38,101 psi | 74% | 2779 fps | 96.3% |
| Alliant Reloder-16 | <<locked>> | 90% | 37,710 psi | 73% | 2825 fps | 95.4% |
| Alliant Reloder-17 | 39.8 gr | 82% | 32,721 psi | 64% | 2720 fps | 95.3% |
| Alliant Reloder-23 | <<locked>> | 98% | 34,316 psi | 67% | 2762 fps | 95.9% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 41,626 psi | 81% | 2851 fps | 96.8% |
| Bofors RP3 | <<locked>> | 80% | 34,751 psi | 67% | 2707 fps | 97% |
| Hodgdon BL-C2 | <<locked>> | 80% | 43,076 psi | 84% | 2884 fps | 99.4% |
| Hodgdon H380 | <<locked>> | 84% | 41,089 psi | 80% | 2835 fps | 95.9% |
| Hodgdon H4895 | <<locked>> | 80% | 42,757 psi | 83% | 2867 fps | 98.5% |
| Hodgdon Hybrid 100V | <<locked>> | 88% | 32,445 psi | 63% | 2654 fps | 95.3% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 38,580 psi | 75% | 2825 fps | 98.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,049 psi | 51% | 1699 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 41,191 psi | 80% | 2818 fps | 98.2% |
| IMR 3031 | <<locked>> | 80% | 42,351 psi | 82% | 2874 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 37,724 psi | 73% | 2726 fps | 96.3% |
| IMR 4831 | <<locked>> | 90% | 36,376 psi | 71% | 2766 fps | 95% |
| IMR 4895 | <<locked>> | 80% | 39,044 psi | 76% | 2812 fps | 97.3% |
| Lovex D073.6 | <<locked>> | 80% | 41,089 psi | 80% | 2831 fps | 99.7% |
| Lovex S060 | <<locked>> | 80% | 42,685 psi | 83% | 2795 fps | 98.1% |
| Lovex S062 | <<locked>> | 80% | 37,507 psi | 73% | 2733 fps | 98.1% |
| Lovex S065 | <<locked>> | 90% | 42,134 psi | 82% | 2828 fps | 95.2% |
| Norma 201 | <<locked>> | 80% | 41,350 psi | 80% | 2808 fps | 98.8% |
| Norma 202 | <<locked>> | 80% | 41,713 psi | 81% | 2822 fps | 99.9% |
| Norma 203B | <<locked>> | 80% | 37,478 psi | 73% | 2766 fps | 96.7% |
| Norma URP | <<locked>> | 90% | 37,942 psi | 74% | 2818 fps | 95.3% |
| Ramshot Big Game | <<locked>> | 80% | 37,028 psi | 72% | 2776 fps | 96.4% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,179 psi | 51% | 1739 fps | 100% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 39,871 psi | 77% | 2884 fps | 96.8% |
| ReloadSwiss RS 60 | 38.8 gr | 80% | 32,518 psi | 63% | 2730 fps | 97.8% |
| ReloadSwiss RS 62 | 44.6 gr | 92% | 40,190 psi | 78% | 2894 fps | 95.9% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 40,538 psi | 79% | 2904 fps | 95% |
| Rottweil R 902 | <<locked>> | 80% | 39,378 psi | 76% | 2756 fps | 98.4% |
| Rottweil R 903 | <<locked>> | 80% | 32,634 psi | 63% | 2644 fps | 95.8% |
| Shooters World Long Rifle | <<locked>> | 90% | 42,134 psi | 82% | 2828 fps | 95.2% |
| Shooters World Match Rifle | <<locked>> | 80% | 41,089 psi | 80% | 2831 fps | 99.7% |
| Shooters World Precision | <<locked>> | 80% | 37,507 psi | 73% | 2733 fps | 98.1% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 33,837 psi | 66% | 2700 fps | 95.3% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 43,279 psi | 84% | 2769 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 42,569 psi | 83% | 2838 fps | 96.2% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 40,944 psi | 80% | 2818 fps | 97.6% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 42,960 psi | 83% | 2772 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 35,520 psi | 69% | 2621 fps | 99.8% |
| Somchem S335 | <<locked>> | 80% | 42,482 psi | 83% | 2772 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 42,351 psi | 82% | 2838 fps | 97.9% |
| Somchem S355 | <<locked>> | 80% | 33,649 psi | 65% | 2657 fps | 96% |
| Somchem S365 | <<locked>> | 86% | 29,602 psi | 57% | 2635 fps | 95.6% |
| Vihtavuori N133 | <<locked>> | 80% | 43,279 psi | 84% | 2769 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 38,682 psi | 75% | 2746 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 39,494 psi | 77% | 2753 fps | 99.9% |
| Vihtavuori N150 | <<locked>> | 80% | 31,995 psi | 62% | 2592 fps | 96.9% |
| Vihtavuori N160 | <<locked>> | 88% | 37,173 psi | 72% | 2762 fps | 95% |
| Vihtavuori N540 | <<locked>> | 80% | 38,000 psi | 74% | 2733 fps | 99.6% |
| Vihtavuori N550 | <<locked>> | 90% | 38,972 psi | 76% | 2818 fps | 95.4% |
| Vihtavuori N555 | <<locked>> | 96% | 34,534 psi | 67% | 2782 fps | 95% |
| Winchester 6.5 StaBALL | <<locked>> | 84% | 32,677 psi | 63% | 2621 fps | 95.6% |
| Winchester StaBALL Match | <<locked>> | 80% | 40,335 psi | 78% | 2822 fps | 98.1% |
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 63 powders for .257 Roberts loaded with the .257 | 100gr | Osprey Virtus. ReloadSwiss RS 60 delivers the highest muzzle velocity at 3,058 fps; across all powders the maximum-charge window runs from 1,900 fps to 3,058 fps. Alliant Reloder-23 gives the best case fill at 100 %, and 63 of the 63 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (355 MPa), the top charges use 68–90 %, 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, Hodgdon TrailBoss, ReloadSwiss RS 14 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. ReloadSwiss RS 60, Alliant Reloder-17, ReloadSwiss RS 62 rank at the top here: for .257 Roberts with the .257 | 100gr | Osprey Virtus 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.