Load Specifications
Load data in caliber .280 Ackley Improved with .287 | 160gr | Woodleigh PP SN bullet and 97 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-17.
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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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 2495 | <<locked>> | 82% | 56,768 psi | 87% | 2680 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 57,653 psi | 89% | 2756 fps | 99.3% |
| Accurate 3100ᴾ | <<locked>> | 100% | 56,115 psi | 86% | 2805 fps | 99.9% |
| Accurate 4064 | <<locked>> | 84% | 57,188 psi | 88% | 2736 fps | 100% |
| Accurate 4350 | <<locked>> | 92% | 58,247 psi | 90% | 2851 fps | 100% |
| Accurate MAGPROᴾ | <<locked>> | 100% | 58,233 psi | 90% | 2949 fps | 97.2% |
| ADI AR 2208 | <<locked>> | 86% | 57,014 psi | 88% | 2769 fps | 100% |
| ADI AR 2209 | <<locked>> | 96% | 55,187 psi | 85% | 2841 fps | 98.6% |
| ADI AR 2213ᴾ | <<locked>> | 100% | 56,507 psi | 87% | 2894 fps | 97.8% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 56,420 psi | 87% | 2890 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 96% | 55,274 psi | 85% | 2838 fps | 98.6% |
| Alliant Power Pro Varmint | <<locked>> | 96% | 55,274 psi | 85% | 2838 fps | 98.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 86% | 58,001 psi | 89% | 2792 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 84% | 58,102 psi | 89% | 2812 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 94% | 58,682 psi | 90% | 2900 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 88% | 56,521 psi | 87% | 2874 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 98% | 58,088 psi | 89% | 2881 fps | 99% |
| Alliant Reloder-22ᴾ | <<locked>> | 100% | 55,506 psi | 85% | 2887 fps | 98.8% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 52,446 psi | 81% | 2815 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 45,571 psi | 70% | 2753 fps | 99.6% |
| Alliant Reloder-26 | <<locked>> | 98% | 56,521 psi | 87% | 2959 fps | 100% |
| Bofors RP15ᴾ | <<locked>> | 100% | 50,952 psi | 78% | 2815 fps | 98% |
| Bofors RP3 | <<locked>> | 84% | 55,376 psi | 85% | 2759 fps | 100% |
| Bofors RP5ᴾ | <<locked>> | 100% | 55,506 psi | 85% | 2887 fps | 98.8% |
| Bofors RP7 | <<locked>> | 90% | 57,899 psi | 89% | 2795 fps | 99.4% |
| Hodgdon H380 | <<locked>> | 84% | 55,521 psi | 85% | 2776 fps | 100% |
| Hodgdon H414 | <<locked>> | 90% | 56,507 psi | 87% | 2848 fps | 99.6% |
| Hodgdon H4350 | <<locked>> | 88% | 56,043 psi | 86% | 2805 fps | 98.9% |
| Hodgdon H4831 | <<locked>> | 98% | 56,753 psi | 87% | 2838 fps | 97.2% |
| Hodgdon H4831 SC | <<locked>> | 98% | 55,550 psi | 85% | 2822 fps | 97% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 55,347 psi | 85% | 2776 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 56,840 psi | 87% | 2808 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 44,730 psi | 69% | 2785 fps | 97.4% |
| Hodgdon Superformance | <<locked>> | 90% | 56,681 psi | 87% | 2887 fps | 99.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,477 psi | 56% | 1716 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 57,290 psi | 88% | 2769 fps | 100% |
| IMR 4064 | <<locked>> | 84% | 56,420 psi | 87% | 2753 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 82% | 55,506 psi | 85% | 2740 fps | 99.5% |
| IMR 4350 | <<locked>> | 92% | 55,651 psi | 86% | 2782 fps | 99.3% |
| IMR 4451 Enduron | <<locked>> | 88% | 56,130 psi | 86% | 2772 fps | 99.5% |
| IMR 4831 | <<locked>> | 94% | 58,334 psi | 90% | 2838 fps | 100% |
| IMR 4895 | <<locked>> | 82% | 56,043 psi | 86% | 2789 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 98% | 58,131 psi | 89% | 2825 fps | 97.6% |
| IMR 7828 SSCᴾ | <<locked>> | 100% | 53,882 psi | 83% | 2864 fps | 97.4% |
| Lovex S060 | <<locked>> | 82% | 57,754 psi | 89% | 2733 fps | 100% |
| Lovex S062 | <<locked>> | 84% | 56,666 psi | 87% | 2743 fps | 100% |
| Lovex S065 | <<locked>> | 90% | 56,420 psi | 87% | 2769 fps | 99.9% |
| Lovex S070 | <<locked>> | 92% | 57,827 psi | 89% | 2812 fps | 99.8% |
| Lovex S071ᴾ | <<locked>> | 100% | 46,441 psi | 71% | 2657 fps | 99.1% |
| Norma 201 | <<locked>> | 82% | 57,986 psi | 89% | 2753 fps | 100% |
| Norma 203B | <<locked>> | 84% | 57,377 psi | 88% | 2799 fps | 100% |
| Norma 204 | <<locked>> | 92% | 56,376 psi | 87% | 2835 fps | 98.6% |
| Norma MRP | <<locked>> | 98% | 55,114 psi | 85% | 2910 fps | 99.6% |
| Norma URP | <<locked>> | 92% | 56,681 psi | 87% | 2835 fps | 100% |
| Ramshot Big Game | <<locked>> | 84% | 58,262 psi | 90% | 2825 fps | 100% |
| Ramshot Grandᴾ | <<locked>> | 100% | 54,462 psi | 84% | 2884 fps | 97.9% |
| Ramshot Hunter | <<locked>> | 92% | 55,332 psi | 85% | 2835 fps | 99.9% |
| Ramshot Magnumᴾ | <<locked>> | 100% | 48,457 psi | 75% | 2756 fps | 98.2% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,188 psi | 57% | 1755 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 84% | 55,506 psi | 85% | 2762 fps | 99.7% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 55,883 psi | 86% | 2864 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 58,131 psi | 89% | 2874 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 56,231 psi | 87% | 2900 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 44,672 psi | 69% | 2782 fps | 98.4% |
| Rottweil R 902 | <<locked>> | 84% | 58,740 psi | 90% | 2756 fps | 100% |
| Rottweil R 903 | <<locked>> | 86% | 55,230 psi | 85% | 2753 fps | 100% |
| Rottweil R 904 | <<locked>> | 96% | 56,913 psi | 88% | 2812 fps | 97.9% |
| Rottweil R 905 | <<locked>> | 98% | 57,624 psi | 89% | 2871 fps | 99% |
| Rottweil R 907 | <<locked>> | 90% | 57,899 psi | 89% | 2795 fps | 99.4% |
| Shooters World Long Rifle | <<locked>> | 90% | 56,420 psi | 87% | 2769 fps | 99.9% |
| Shooters World Precision | <<locked>> | 84% | 56,666 psi | 87% | 2743 fps | 100% |
| Shooters World SW4350 | <<locked>> | 92% | 57,827 psi | 89% | 2812 fps | 99.8% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 56,840 psi | 87% | 2812 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 57,725 psi | 89% | 2785 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 82% | 58,726 psi | 90% | 2680 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 56,275 psi | 87% | 2641 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 90% | 55,999 psi | 86% | 2726 fps | 99.5% |
| SNPE Vectan Tubal 8000 | <<locked>> | 98% | 57,130 psi | 88% | 2867 fps | 98.9% |
| Somchem S335 | <<locked>> | 82% | 58,320 psi | 90% | 2677 fps | 100% |
| Somchem S355 | <<locked>> | 86% | 55,347 psi | 85% | 2753 fps | 100% |
| Somchem S361 | <<locked>> | 96% | 58,639 psi | 90% | 2805 fps | 97.4% |
| Somchem S365 | <<locked>> | 94% | 56,173 psi | 86% | 2835 fps | 100% |
| Somchem S385 | <<locked>> | 98% | 58,204 psi | 90% | 2848 fps | 99.5% |
| Vihtavuori N135 | <<locked>> | 82% | 55,738 psi | 86% | 2664 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 55,637 psi | 86% | 2677 fps | 100% |
| Vihtavuori N150 | <<locked>> | 88% | 56,666 psi | 87% | 2726 fps | 100% |
| Vihtavuori N160 | <<locked>> | 90% | 55,230 psi | 85% | 2776 fps | 100% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 53,911 psi | 83% | 2769 fps | 98.8% |
| Vihtavuori N540 | <<locked>> | 84% | 57,392 psi | 88% | 2723 fps | 100% |
| Vihtavuori N550 | <<locked>> | 92% | 57,827 psi | 89% | 2831 fps | 100% |
| Vihtavuori N555 | <<locked>> | 98% | 55,259 psi | 85% | 2844 fps | 100% |
| Vihtavuori N560 | <<locked>> | 98% | 55,332 psi | 85% | 2904 fps | 97.3% |
| Winchester 6.5 StaBALL | <<locked>> | 92% | 58,334 psi | 90% | 2789 fps | 100% |
| Winchester 760 | <<locked>> | 90% | 56,507 psi | 87% | 2848 fps | 99.6% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 47,688 psi | 73% | 2881 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 82% | 58,044 psi | 89% | 2792 fps | 100% |
| Winchester Supreme 780ᴾ | <<locked>> | 100% | 58,320 psi | 90% | 2841 fps | 98.9% |
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 2495 | <<locked>> | 80% | 53,200 psi | 82% | 2635 fps | 100% |
| Accurate 2700 | <<locked>> | 80% | 50,720 psi | 78% | 2651 fps | 98.4% |
| Accurate 3100 | <<locked>> | 84% | 32,576 psi | 50% | 2375 fps | 95.4% |
| Accurate 4064 | <<locked>> | 80% | 50,444 psi | 78% | 2644 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 38,725 psi | 60% | 2526 fps | 98.9% |
| Accurate MAGPRO | <<locked>> | 96% | 50,517 psi | 78% | 2825 fps | 95.5% |
| ADI AR 2208 | <<locked>> | 80% | 47,311 psi | 73% | 2618 fps | 100% |
| ADI AR 2209 | <<locked>> | 88% | 42,453 psi | 65% | 2612 fps | 95.8% |
| ADI AR 2213 | <<locked>> | 94% | 46,209 psi | 71% | 2713 fps | 95.3% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 52,547 psi | 81% | 2831 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 86% | 39,972 psi | 61% | 2559 fps | 95% |
| Alliant Power Pro Varmint | <<locked>> | 86% | 39,972 psi | 61% | 2559 fps | 95% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 48,109 psi | 74% | 2644 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 51,329 psi | 79% | 2713 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 80% | 37,550 psi | 58% | 2533 fps | 98.9% |
| Alliant Reloder-17 | 51.1 gr | 80% | 42,467 psi | 65% | 2651 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 86% | 39,610 psi | 61% | 2552 fps | 95% |
| Alliant Reloder-22 | <<locked>> | 90% | 39,914 psi | 61% | 2605 fps | 95.2% |
| Alliant Reloder-23 | <<locked>> | 80% | 27,586 psi | 42% | 2300 fps | 97% |
| Alliant Reloder-25 | <<locked>> | 88% | 31,140 psi | 48% | 2411 fps | 95.2% |
| Alliant Reloder-26 | 52.4 gr | 80% | 29,399 psi | 45% | 2402 fps | 95.3% |
| Bofors RP15 | <<locked>> | 94% | 42,003 psi | 65% | 2648 fps | 95.8% |
| Bofors RP3 | <<locked>> | 80% | 48,472 psi | 75% | 2657 fps | 100% |
| Bofors RP5 | <<locked>> | 90% | 39,914 psi | 61% | 2605 fps | 95.2% |
| Bofors RP7 | <<locked>> | 80% | 42,583 psi | 66% | 2539 fps | 97% |
| Hodgdon H380 | <<locked>> | 80% | 48,660 psi | 75% | 2667 fps | 99.8% |
| Hodgdon H414 | <<locked>> | 80% | 40,466 psi | 62% | 2566 fps | 97% |
| Hodgdon H4350 | <<locked>> | 80% | 43,468 psi | 67% | 2589 fps | 96.5% |
| Hodgdon H4831 | <<locked>> | 94% | 49,559 psi | 76% | 2723 fps | 95.6% |
| Hodgdon H4831 SC | <<locked>> | 94% | 48,486 psi | 75% | 2703 fps | 95.3% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 35,157 psi | 54% | 2431 fps | 99.3% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 53,098 psi | 82% | 2753 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 39,204 psi | 60% | 2657 fps | 95.3% |
| Hodgdon Superformance | <<locked>> | 80% | 39,508 psi | 61% | 2582 fps | 96.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,267 psi | 42% | 1532 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 53,824 psi | 83% | 2720 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 49,748 psi | 77% | 2651 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 80% | 51,924 psi | 80% | 2680 fps | 99.1% |
| IMR 4350 | <<locked>> | 80% | 38,145 psi | 59% | 2467 fps | 95.7% |
| IMR 4451 Enduron | <<locked>> | 80% | 43,932 psi | 68% | 2566 fps | 97.7% |
| IMR 4831 | <<locked>> | 80% | 37,028 psi | 57% | 2477 fps | 98.6% |
| IMR 4895 | <<locked>> | 80% | 52,678 psi | 81% | 2740 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 48,327 psi | 74% | 2664 fps | 95.5% |
| IMR 7828 SSC | <<locked>> | 96% | 47,253 psi | 73% | 2746 fps | 95.8% |
| Lovex S060 | <<locked>> | 80% | 54,302 psi | 84% | 2684 fps | 100% |
| Lovex S062 | <<locked>> | 80% | 50,038 psi | 77% | 2648 fps | 100% |
| Lovex S065 | <<locked>> | 80% | 41,481 psi | 64% | 2516 fps | 98.4% |
| Lovex S070 | <<locked>> | 80% | 39,624 psi | 61% | 2497 fps | 97% |
| Lovex S071 | <<locked>> | 88% | 31,676 psi | 49% | 2352 fps | 95% |
| Norma 201 | <<locked>> | 80% | 54,476 psi | 84% | 2703 fps | 100% |
| Norma 203B | <<locked>> | 80% | 50,691 psi | 78% | 2700 fps | 100% |
| Norma 204 | <<locked>> | 84% | 43,105 psi | 66% | 2605 fps | 95.8% |
| Norma MRP | <<locked>> | 86% | 36,463 psi | 56% | 2556 fps | 95.6% |
| Norma URP | <<locked>> | 80% | 38,290 psi | 59% | 2516 fps | 98.7% |
| Ramshot Big Game | <<locked>> | 80% | 50,923 psi | 78% | 2720 fps | 100% |
| Ramshot Grand | <<locked>> | 94% | 43,990 psi | 68% | 2694 fps | 95.2% |
| Ramshot Hunter | <<locked>> | 80% | 37,260 psi | 57% | 2507 fps | 97% |
| Ramshot Magnum | <<locked>> | 94% | 39,131 psi | 60% | 2575 fps | 95.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,775 psi | 43% | 1568 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 48,602 psi | 75% | 2654 fps | 99.1% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 45,121 psi | 69% | 2700 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 38,406 psi | 59% | 2543 fps | 98.6% |
| ReloadSwiss RS 70 | 51.9 gr | 80% | 37,057 psi | 57% | 2546 fps | 98% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 36,260 psi | 56% | 2582 fps | 95.2% |
| Rottweil R 902 | <<locked>> | 80% | 51,909 psi | 80% | 2661 fps | 100% |
| Rottweil R 903 | <<locked>> | 80% | 45,571 psi | 70% | 2605 fps | 100% |
| Rottweil R 904 | <<locked>> | 88% | 44,164 psi | 68% | 2595 fps | 95% |
| Rottweil R 905 | <<locked>> | 88% | 41,278 psi | 64% | 2592 fps | 95.7% |
| Rottweil R 907 | <<locked>> | 80% | 42,583 psi | 66% | 2539 fps | 97% |
| Shooters World Long Rifle | <<locked>> | 80% | 41,481 psi | 64% | 2516 fps | 98.4% |
| Shooters World Precision | <<locked>> | 80% | 50,038 psi | 77% | 2648 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 39,624 psi | 61% | 2497 fps | 97% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 46,847 psi | 72% | 2657 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 54,302 psi | 84% | 2736 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 55,100 psi | 85% | 2635 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 46,731 psi | 72% | 2510 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 40,611 psi | 62% | 2464 fps | 97.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 40,930 psi | 63% | 2589 fps | 95.6% |
| Somchem S335 | <<locked>> | 80% | 54,926 psi | 85% | 2635 fps | 100% |
| Somchem S355 | <<locked>> | 80% | 45,847 psi | 71% | 2602 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 48,095 psi | 74% | 2641 fps | 95.2% |
| Somchem S365 | <<locked>> | 80% | 34,853 psi | 54% | 2477 fps | 99.9% |
| Somchem S385 | <<locked>> | 84% | 36,941 psi | 57% | 2470 fps | 95.2% |
| Vihtavuori N135 | <<locked>> | 80% | 52,272 psi | 80% | 2621 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 52,315 psi | 80% | 2635 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 43,714 psi | 67% | 2533 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 39,842 psi | 61% | 2516 fps | 98.9% |
| Vihtavuori N165 | <<locked>> | 90% | 38,812 psi | 60% | 2503 fps | 95.4% |
| Vihtavuori N540 | <<locked>> | 80% | 50,546 psi | 78% | 2628 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 39,146 psi | 60% | 2516 fps | 98.7% |
| Vihtavuori N555 | <<locked>> | 80% | 30,501 psi | 47% | 2372 fps | 97.1% |
| Vihtavuori N560 | <<locked>> | 94% | 48,414 psi | 74% | 2785 fps | 95.7% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 38,856 psi | 60% | 2487 fps | 99.9% |
| Winchester 760 | <<locked>> | 80% | 40,683 psi | 63% | 2572 fps | 97.1% |
| Winchester StaBALL HD | <<locked>> | 80% | 24,439 psi | 38% | 2270 fps | 95.8% |
| Winchester StaBALL Match | <<locked>> | 80% | 54,288 psi | 84% | 2740 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 41,307 psi | 64% | 2559 fps | 95.5% |
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 97 powders for .280 Ackley Improved loaded with the .287 | 160gr | Woodleigh PP SN. Alliant Reloder-26 delivers the highest muzzle velocity at 2,959 fps; across all powders the maximum-charge window runs from 1,716 fps to 2,959 fps. Accurate 3100 gives the best case fill at 100 %, and 97 of the 97 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (448 MPa), the top charges use 56–90 %, leaving at least 10 % headroom. The 160.0 gr projectile in 0.287" calls for a 1:12.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, Accurate MAGPRO, ADI AR 2213 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-17 rank at the top here: for .280 Ackley Improved with the .287 | 160gr | Woodleigh PP SN 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.