Load Specifications
Load data in caliber .257 Ackley Improved with .257 | 52gr | Peregrine VRG-3 bullet and 43 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are IMR 3031, Accurate 4064 and Vihtavuori N135.
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 2015 | <<locked>> | 86% | 43,352 psi | 90% | 3707 fps | 99% |
| Accurate 2015 | <<locked>> | 86% | 42,250 psi | 88% | 3688 fps | 98.8% |
| Accurate 2460 | <<locked>> | 82% | 41,655 psi | 86% | 3668 fps | 96% |
| Accurate 2495 | <<locked>> | 92% | 43,062 psi | 89% | 3737 fps | 99.2% |
| Accurate 2495 | <<locked>> | 92% | 41,582 psi | 86% | 3707 fps | 99% |
| Accurate 4064 | <<locked>> | 94% | 43,120 psi | 89% | 3757 fps | 97.2% |
| Accurate 4064 | <<locked>> | 94% | 41,727 psi | 87% | 3724 fps | 96.8% |
| Alliant AR-Comp | <<locked>> | 88% | 43,352 psi | 90% | 3812 fps | 100% |
| Alliant AR-Comp | <<locked>> | 88% | 42,395 psi | 88% | 3789 fps | 100% |
| Alliant Reloder-10x | <<locked>> | 82% | 43,265 psi | 90% | 3747 fps | 99.5% |
| Alliant Reloder-10x | <<locked>> | 82% | 42,293 psi | 88% | 3730 fps | 99.4% |
| Hodgdon H322 | <<locked>> | 82% | 42,221 psi | 88% | 3740 fps | 97.4% |
| Hodgdon H322 | <<locked>> | 82% | 41,336 psi | 86% | 3717 fps | 97.2% |
| Hodgdon H335 | <<locked>> | 82% | 43,468 psi | 90% | 3747 fps | 96.8% |
| Hodgdon H335 | <<locked>> | 82% | 42,554 psi | 88% | 3727 fps | 96.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 32,996 psi | 68% | 2631 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 32,735 psi | 68% | 2631 fps | 100% |
| IMR 3031 | <<locked>> | 88% | 41,408 psi | 86% | 3776 fps | 98% |
| IMR 3031 | <<locked>> | 90% | 43,178 psi | 90% | 3825 fps | 98.5% |
| IMR 4198 | <<locked>> | 82% | 43,323 psi | 90% | 3734 fps | 99.9% |
| Norma 202 | <<locked>> | 88% | 41,887 psi | 87% | 3704 fps | 96.4% |
| Norma 202 | <<locked>> | 88% | 40,944 psi | 85% | 3684 fps | 96.1% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 33,141 psi | 69% | 2690 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 32,793 psi | 68% | 2687 fps | 100% |
| Rottweil R 901 | <<locked>> | 86% | 42,801 psi | 89% | 3704 fps | 96.2% |
| Rottweil R 901 | <<locked>> | 86% | 41,597 psi | 86% | 3678 fps | 95.9% |
| SNPE Vectan SP 3 | <<locked>> | 82% | 42,960 psi | 89% | 3743 fps | 98.3% |
| SNPE Vectan Tubal 3000 | <<locked>> | 86% | 41,205 psi | 85% | 3602 fps | 96.1% |
| SNPE Vectan Tubal 3000 | <<locked>> | 88% | 43,221 psi | 90% | 3658 fps | 96.7% |
| SNPE Vectan Tubal 5000 | <<locked>> | 92% | 40,669 psi | 84% | 3586 fps | 97.2% |
| SNPE Vectan Tubal 5000 | <<locked>> | 94% | 42,757 psi | 89% | 3642 fps | 97.8% |
| Somchem S335 | <<locked>> | 88% | 43,192 psi | 90% | 3661 fps | 97.6% |
| Somchem S335 | <<locked>> | 88% | 42,206 psi | 88% | 3642 fps | 97.4% |
| Vihtavuori N130 | <<locked>> | 82% | 41,060 psi | 85% | 3619 fps | 99.1% |
| Vihtavuori N130 | <<locked>> | 84% | 43,033 psi | 89% | 3675 fps | 99.4% |
| Vihtavuori N133 | <<locked>> | 86% | 41,002 psi | 85% | 3619 fps | 98.5% |
| Vihtavuori N133 | <<locked>> | 88% | 43,062 psi | 89% | 3671 fps | 98.9% |
| Vihtavuori N135 | <<locked>> | 92% | 43,178 psi | 90% | 3747 fps | 99.1% |
| Vihtavuori N135 | <<locked>> | 92% | 42,148 psi | 87% | 3727 fps | 99% |
| Vihtavuori N140 | <<locked>> | 90% | 42,511 psi | 88% | 3684 fps | 97% |
| Vihtavuori N140 | <<locked>> | 90% | 41,597 psi | 86% | 3665 fps | 96.8% |
| Vihtavuori N540 | <<locked>> | 90% | 41,234 psi | 86% | 3652 fps | 96.1% |
| Vihtavuori N540 | <<locked>> | 92% | 43,149 psi | 90% | 3704 fps | 96.7% |
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 2015 | <<locked>> | 80% | 35,389 psi | 73% | 3494 fps | 97% |
| Accurate 2015 | <<locked>> | 80% | 34,360 psi | 71% | 3468 fps | 96.6% |
| Accurate 2460 | <<locked>> | 80% | 38,856 psi | 81% | 3593 fps | 95% |
| Accurate 2495 | <<locked>> | 82% | 30,168 psi | 63% | 3363 fps | 95.2% |
| Accurate 2495 | <<locked>> | 84% | 31,038 psi | 64% | 3399 fps | 95.6% |
| Accurate 4064 | 49.8 gr | 90% | 37,550 psi | 78% | 3606 fps | 95.4% |
| Accurate 4064 | 49.8 gr | 92% | 38,856 psi | 81% | 3648 fps | 95.9% |
| Alliant AR-Comp | <<locked>> | 80% | 32,648 psi | 68% | 3514 fps | 98.6% |
| Alliant AR-Comp | <<locked>> | 80% | 31,720 psi | 66% | 3484 fps | 98.3% |
| Alliant Reloder-10x | <<locked>> | 80% | 40,625 psi | 84% | 3681 fps | 99.1% |
| Alliant Reloder-10x | <<locked>> | 80% | 39,624 psi | 82% | 3661 fps | 99% |
| Hodgdon H322 | <<locked>> | 80% | 39,349 psi | 82% | 3661 fps | 96.5% |
| Hodgdon H322 | <<locked>> | 80% | 38,493 psi | 80% | 3638 fps | 96.2% |
| Hodgdon H335 | <<locked>> | 80% | 40,422 psi | 84% | 3665 fps | 95.8% |
| Hodgdon H335 | <<locked>> | 80% | 39,508 psi | 82% | 3645 fps | 95.5% |
| Hodgdon TrailBoss | <<locked>> | 80% | 24,323 psi | 50% | 2375 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 24,033 psi | 50% | 2372 fps | 100% |
| IMR 3031 | 43.8 gr | 82% | 33,373 psi | 69% | 3537 fps | 95.2% |
| IMR 3031 | 44.9 gr | 84% | 34,896 psi | 72% | 3593 fps | 95.9% |
| IMR 4198 | <<locked>> | 80% | 40,640 psi | 84% | 3665 fps | 99.6% |
| Norma 202 | <<locked>> | 86% | 39,160 psi | 81% | 3632 fps | 95.5% |
| Norma 202 | <<locked>> | 86% | 38,159 psi | 79% | 3606 fps | 95.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 24,337 psi | 50% | 2428 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 23,975 psi | 50% | 2421 fps | 100% |
| Rottweil R 901 | <<locked>> | 84% | 40,292 psi | 84% | 3638 fps | 95.4% |
| Rottweil R 901 | <<locked>> | 84% | 39,088 psi | 81% | 3612 fps | 95% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 40,263 psi | 84% | 3675 fps | 97.6% |
| SNPE Vectan Tubal 3000 | <<locked>> | 84% | 38,696 psi | 80% | 3533 fps | 95.2% |
| SNPE Vectan Tubal 3000 | <<locked>> | 86% | 40,321 psi | 84% | 3583 fps | 95.8% |
| SNPE Vectan Tubal 5000 | <<locked>> | 88% | 35,868 psi | 74% | 3455 fps | 95.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 88% | 35,056 psi | 73% | 3435 fps | 95.3% |
| Somchem S335 | <<locked>> | 82% | 35,650 psi | 74% | 3458 fps | 95.2% |
| Somchem S335 | <<locked>> | 84% | 37,115 psi | 77% | 3504 fps | 95.8% |
| Vihtavuori N130 | <<locked>> | 80% | 38,580 psi | 80% | 3556 fps | 98.6% |
| Vihtavuori N130 | <<locked>> | 80% | 37,710 psi | 78% | 3537 fps | 98.5% |
| Vihtavuori N133 | <<locked>> | 80% | 33,750 psi | 70% | 3415 fps | 96.3% |
| Vihtavuori N133 | <<locked>> | 80% | 32,938 psi | 68% | 3392 fps | 96% |
| Vihtavuori N135 | 42.9 gr | 82% | 30,705 psi | 64% | 3392 fps | 95.3% |
| Vihtavuori N135 | 44 gr | 84% | 32,053 psi | 67% | 3442 fps | 95.9% |
| Vihtavuori N140 | <<locked>> | 86% | 37,101 psi | 77% | 3540 fps | 95.2% |
| Vihtavuori N140 | <<locked>> | 88% | 38,827 psi | 81% | 3593 fps | 95.9% |
| Vihtavuori N540 | <<locked>> | 88% | 38,595 psi | 80% | 3579 fps | 95.2% |
| Vihtavuori N540 | <<locked>> | 90% | 40,335 psi | 84% | 3632 fps | 95.8% |
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 115 powders for .257 Ackley Improved loaded with the .257 | 52gr | Peregrine VRG-3. IMR 3031 delivers the highest muzzle velocity at 3,825 fps; across all powders the maximum-charge window runs from 2,631 fps to 3,825 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 115 of the 115 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (332 MPa), the top charges use 68–90 %, leaving at least 10 % headroom. Hodgdon TrailBoss, 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. IMR 3031, Accurate 4064, Vihtavuori N135 rank at the top here: for .257 Ackley Improved with the .257 | 52gr | Peregrine VRG-3 they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, ADI AR 2206H, ADI AR 2206H, ADI Benchmark 8208 burn incompletely and react more sensitively to barrel length and temperature. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.