Load Specifications
Load data in caliber .280 Ackley Improved with .284 | 160gr | Sierra SBT GameKing 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% | 56,913 psi | 88% | 2684 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 57,812 psi | 89% | 2759 fps | 99.3% |
| Accurate 3100ᴾ | <<locked>> | 100% | 55,912 psi | 86% | 2805 fps | 99.9% |
| Accurate 4064 | <<locked>> | 84% | 57,348 psi | 88% | 2740 fps | 100% |
| Accurate 4350 | <<locked>> | 92% | 58,073 psi | 89% | 2851 fps | 100% |
| Accurate MAGPROᴾ | <<locked>> | 100% | 58,407 psi | 90% | 2953 fps | 97.3% |
| ADI AR 2208 | <<locked>> | 86% | 56,840 psi | 87% | 2769 fps | 100% |
| ADI AR 2209 | <<locked>> | 96% | 55,361 psi | 85% | 2844 fps | 98.6% |
| ADI AR 2213ᴾ | <<locked>> | 100% | 56,594 psi | 87% | 2897 fps | 97.8% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 56,565 psi | 87% | 2894 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 86% | 57,870 psi | 89% | 2792 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 84% | 58,276 psi | 90% | 2818 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 92% | 55,216 psi | 85% | 2854 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 88% | 56,376 psi | 87% | 2871 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 98% | 58,233 psi | 90% | 2884 fps | 99% |
| Alliant Reloder-22ᴾ | <<locked>> | 100% | 55,680 psi | 86% | 2890 fps | 98.8% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 52,634 psi | 81% | 2818 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 45,716 psi | 70% | 2756 fps | 99.6% |
| Alliant Reloder-26 | <<locked>> | 98% | 56,710 psi | 87% | 2963 fps | 100% |
| Bofors RP15ᴾ | <<locked>> | 100% | 51,111 psi | 79% | 2818 fps | 98% |
| Bofors RP3 | <<locked>> | 84% | 55,245 psi | 85% | 2759 fps | 100% |
| Bofors RP5ᴾ | <<locked>> | 100% | 55,680 psi | 86% | 2890 fps | 98.8% |
| Bofors RP7 | <<locked>> | 90% | 58,059 psi | 89% | 2802 fps | 99.5% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 45,281 psi | 70% | 2690 fps | 96% |
| Hodgdon H380 | <<locked>> | 84% | 55,666 psi | 86% | 2779 fps | 100% |
| Hodgdon H414 | <<locked>> | 90% | 56,637 psi | 87% | 2851 fps | 99.7% |
| Hodgdon H4350 | <<locked>> | 88% | 56,173 psi | 86% | 2808 fps | 98.9% |
| Hodgdon H4831 | <<locked>> | 98% | 56,927 psi | 88% | 2841 fps | 97.2% |
| Hodgdon H4831 SC | <<locked>> | 98% | 55,695 psi | 86% | 2822 fps | 97% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 55,506 psi | 85% | 2776 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 57,014 psi | 88% | 2808 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 44,831 psi | 69% | 2792 fps | 97.5% |
| Hodgdon Superformance | <<locked>> | 90% | 56,855 psi | 87% | 2890 fps | 99.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,651 psi | 56% | 1719 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 57,435 psi | 88% | 2772 fps | 100% |
| IMR 4064 | <<locked>> | 84% | 56,594 psi | 87% | 2756 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 82% | 55,376 psi | 85% | 2736 fps | 99.5% |
| IMR 4350 | <<locked>> | 92% | 55,521 psi | 85% | 2782 fps | 99.3% |
| IMR 4451 Enduron | <<locked>> | 88% | 56,318 psi | 87% | 2779 fps | 99.5% |
| IMR 4831 | <<locked>> | 94% | 58,465 psi | 90% | 2841 fps | 100% |
| IMR 4895 | <<locked>> | 82% | 55,927 psi | 86% | 2789 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 98% | 58,233 psi | 90% | 2828 fps | 97.6% |
| IMR 7828 SSCᴾ | <<locked>> | 100% | 53,969 psi | 83% | 2867 fps | 97.4% |
| Lovex S060 | <<locked>> | 82% | 57,928 psi | 89% | 2736 fps | 100% |
| Lovex S062 | <<locked>> | 84% | 56,840 psi | 87% | 2746 fps | 100% |
| Lovex S065 | <<locked>> | 90% | 56,289 psi | 87% | 2769 fps | 99.9% |
| Lovex S070 | <<locked>> | 92% | 57,682 psi | 89% | 2815 fps | 99.8% |
| Lovex S071ᴾ | <<locked>> | 100% | 46,586 psi | 72% | 2664 fps | 99.1% |
| Norma 201 | <<locked>> | 82% | 58,146 psi | 89% | 2756 fps | 100% |
| Norma 202 | <<locked>> | 82% | 58,711 psi | 90% | 2746 fps | 100% |
| Norma 203B | <<locked>> | 84% | 57,551 psi | 89% | 2802 fps | 100% |
| Norma 204 | <<locked>> | 92% | 56,492 psi | 87% | 2838 fps | 98.6% |
| Norma MRP | <<locked>> | 98% | 55,288 psi | 85% | 2917 fps | 99.6% |
| Norma URP | <<locked>> | 92% | 56,536 psi | 87% | 2831 fps | 100% |
| Ramshot Big Game | <<locked>> | 84% | 58,392 psi | 90% | 2828 fps | 100% |
| Ramshot Grandᴾ | <<locked>> | 100% | 54,592 psi | 84% | 2890 fps | 97.9% |
| Ramshot Hunter | <<locked>> | 92% | 55,506 psi | 85% | 2838 fps | 99.9% |
| Ramshot Magnumᴾ | <<locked>> | 100% | 48,602 psi | 75% | 2762 fps | 98.3% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,362 psi | 57% | 1759 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 84% | 55,376 psi | 85% | 2762 fps | 99.7% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 56,086 psi | 86% | 2867 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 57,972 psi | 89% | 2874 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 56,405 psi | 87% | 2904 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 44,744 psi | 69% | 2785 fps | 98.4% |
| Rottweil R 902 | <<locked>> | 84% | 58,639 psi | 90% | 2756 fps | 100% |
| Rottweil R 903 | <<locked>> | 86% | 55,405 psi | 85% | 2756 fps | 100% |
| Rottweil R 904 | <<locked>> | 96% | 57,058 psi | 88% | 2815 fps | 97.9% |
| Rottweil R 905 | <<locked>> | 98% | 57,740 psi | 89% | 2874 fps | 99% |
| Rottweil R 907 | <<locked>> | 90% | 58,059 psi | 89% | 2802 fps | 99.5% |
| Shooters World Long Rifle | <<locked>> | 90% | 56,289 psi | 87% | 2769 fps | 99.9% |
| Shooters World Precision | <<locked>> | 84% | 56,840 psi | 87% | 2746 fps | 100% |
| Shooters World SW4350 | <<locked>> | 92% | 57,682 psi | 89% | 2815 fps | 99.8% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 56,971 psi | 88% | 2815 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 57,885 psi | 89% | 2785 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 82% | 58,610 psi | 90% | 2680 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 56,115 psi | 86% | 2641 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 90% | 55,825 psi | 86% | 2726 fps | 99.5% |
| SNPE Vectan Tubal 8000 | <<locked>> | 98% | 57,246 psi | 88% | 2871 fps | 99% |
| Somchem S335 | <<locked>> | 82% | 58,465 psi | 90% | 2680 fps | 100% |
| Somchem S355 | <<locked>> | 88% | 58,711 psi | 90% | 2799 fps | 100% |
| Somchem S361 | <<locked>> | 96% | 58,798 psi | 90% | 2808 fps | 97.5% |
| Somchem S365 | <<locked>> | 94% | 56,304 psi | 87% | 2838 fps | 100% |
| Somchem S385 | <<locked>> | 98% | 58,378 psi | 90% | 2851 fps | 99.5% |
| Vihtavuori N135 | <<locked>> | 82% | 55,622 psi | 86% | 2667 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 55,840 psi | 86% | 2684 fps | 100% |
| Vihtavuori N150 | <<locked>> | 88% | 56,550 psi | 87% | 2726 fps | 100% |
| Vihtavuori N160 | <<locked>> | 92% | 58,697 psi | 90% | 2825 fps | 100% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 53,751 psi | 83% | 2769 fps | 98.8% |
| Vihtavuori N540 | <<locked>> | 84% | 57,566 psi | 89% | 2726 fps | 100% |
| Vihtavuori N550 | <<locked>> | 92% | 57,943 psi | 89% | 2835 fps | 100% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 58,784 psi | 90% | 2894 fps | 100% |
| Vihtavuori N560 | <<locked>> | 98% | 55,492 psi | 85% | 2907 fps | 97.4% |
| Winchester 6.5 StaBALL | <<locked>> | 92% | 58,465 psi | 90% | 2792 fps | 100% |
| Winchester 760 | <<locked>> | 90% | 56,637 psi | 87% | 2851 fps | 99.7% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 47,863 psi | 74% | 2884 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 82% | 58,175 psi | 89% | 2795 fps | 100% |
| Winchester Supreme 780ᴾ | <<locked>> | 100% | 58,494 psi | 90% | 2844 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% | 53,359 psi | 82% | 2638 fps | 100% |
| Accurate 2700 | <<locked>> | 80% | 50,604 psi | 78% | 2651 fps | 98.4% |
| Accurate 3100 | <<locked>> | 84% | 32,677 psi | 50% | 2379 fps | 95.5% |
| Accurate 4064 | <<locked>> | 80% | 50,589 psi | 78% | 2648 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 38,667 psi | 59% | 2526 fps | 98.9% |
| Accurate MAGPRO | <<locked>> | 96% | 50,676 psi | 78% | 2831 fps | 95.6% |
| ADI AR 2208 | <<locked>> | 80% | 47,471 psi | 73% | 2625 fps | 100% |
| ADI AR 2209 | <<locked>> | 88% | 42,583 psi | 66% | 2618 fps | 95.8% |
| ADI AR 2213 | <<locked>> | 94% | 46,354 psi | 71% | 2717 fps | 95.4% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 52,692 psi | 81% | 2835 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 48,008 psi | 74% | 2644 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 51,213 psi | 79% | 2713 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 80% | 37,666 psi | 58% | 2539 fps | 99% |
| Alliant Reloder-17 | 51.2 gr | 80% | 42,627 psi | 66% | 2654 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 86% | 39,711 psi | 61% | 2559 fps | 95% |
| Alliant Reloder-22 | <<locked>> | 90% | 39,856 psi | 61% | 2605 fps | 95.3% |
| Alliant Reloder-23 | <<locked>> | 80% | 27,688 psi | 43% | 2303 fps | 97.1% |
| Alliant Reloder-25 | <<locked>> | 88% | 31,256 psi | 48% | 2415 fps | 95.3% |
| Alliant Reloder-26 | 52.5 gr | 80% | 29,472 psi | 45% | 2405 fps | 95.3% |
| Bofors RP15 | <<locked>> | 94% | 41,887 psi | 64% | 2644 fps | 95.8% |
| Bofors RP3 | <<locked>> | 80% | 48,646 psi | 75% | 2661 fps | 100% |
| Bofors RP5 | <<locked>> | 90% | 39,856 psi | 61% | 2605 fps | 95.3% |
| Bofors RP7 | <<locked>> | 80% | 42,525 psi | 65% | 2539 fps | 97% |
| Hodgdon H1000 | <<locked>> | 98% | 42,424 psi | 65% | 2631 fps | 95% |
| Hodgdon H380 | <<locked>> | 80% | 48,805 psi | 75% | 2671 fps | 99.8% |
| Hodgdon H414 | <<locked>> | 80% | 40,582 psi | 62% | 2569 fps | 97.1% |
| Hodgdon H4350 | <<locked>> | 80% | 43,584 psi | 67% | 2592 fps | 96.6% |
| Hodgdon H4831 | <<locked>> | 94% | 49,661 psi | 76% | 2726 fps | 95.7% |
| Hodgdon H4831 SC | <<locked>> | 94% | 48,617 psi | 75% | 2707 fps | 95.4% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 35,085 psi | 54% | 2428 fps | 99.3% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 53,243 psi | 82% | 2759 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 39,334 psi | 61% | 2664 fps | 95.4% |
| Hodgdon Superformance | <<locked>> | 80% | 39,407 psi | 61% | 2579 fps | 96.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,441 psi | 42% | 1535 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 53,998 psi | 83% | 2723 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 49,908 psi | 77% | 2654 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 80% | 52,083 psi | 80% | 2684 fps | 99.2% |
| IMR 4350 | <<locked>> | 80% | 38,261 psi | 59% | 2470 fps | 95.8% |
| IMR 4451 Enduron | <<locked>> | 80% | 43,845 psi | 67% | 2566 fps | 97.7% |
| IMR 4831 | <<locked>> | 80% | 37,130 psi | 57% | 2480 fps | 98.6% |
| IMR 4895 | <<locked>> | 80% | 52,562 psi | 81% | 2740 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 92% | 48,211 psi | 74% | 2664 fps | 95.5% |
| IMR 7828 SSC | <<locked>> | 96% | 47,166 psi | 73% | 2746 fps | 95.8% |
| Lovex S060 | <<locked>> | 80% | 54,476 psi | 84% | 2687 fps | 100% |
| Lovex S062 | <<locked>> | 80% | 50,212 psi | 77% | 2651 fps | 100% |
| Lovex S065 | <<locked>> | 80% | 41,582 psi | 64% | 2523 fps | 98.4% |
| Lovex S070 | <<locked>> | 80% | 39,769 psi | 61% | 2503 fps | 97% |
| Lovex S071 | <<locked>> | 88% | 31,792 psi | 49% | 2359 fps | 95.1% |
| Norma 201 | <<locked>> | 80% | 54,665 psi | 84% | 2707 fps | 100% |
| Norma 202 | <<locked>> | 80% | 55,172 psi | 85% | 2700 fps | 100% |
| Norma 203B | <<locked>> | 80% | 50,589 psi | 78% | 2700 fps | 100% |
| Norma 204 | <<locked>> | 82% | 40,321 psi | 62% | 2549 fps | 95% |
| Norma MRP | <<locked>> | 86% | 36,564 psi | 56% | 2562 fps | 95.6% |
| Norma URP | <<locked>> | 80% | 38,435 psi | 59% | 2520 fps | 98.7% |
| Ramshot Big Game | <<locked>> | 80% | 51,053 psi | 79% | 2723 fps | 100% |
| Ramshot Grand | <<locked>> | 94% | 44,092 psi | 68% | 2700 fps | 95.2% |
| Ramshot Hunter | <<locked>> | 80% | 37,173 psi | 57% | 2507 fps | 96.9% |
| Ramshot Magnum | <<locked>> | 94% | 39,015 psi | 60% | 2575 fps | 95.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,934 psi | 43% | 1572 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 48,762 psi | 75% | 2657 fps | 99.1% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 45,252 psi | 70% | 2703 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 38,508 psi | 59% | 2546 fps | 98.6% |
| ReloadSwiss RS 70 | 52 gr | 80% | 37,188 psi | 57% | 2549 fps | 98.1% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 36,187 psi | 56% | 2582 fps | 95.3% |
| Rottweil R 902 | <<locked>> | 80% | 52,040 psi | 80% | 2661 fps | 100% |
| Rottweil R 903 | <<locked>> | 80% | 45,716 psi | 70% | 2608 fps | 100% |
| Rottweil R 904 | <<locked>> | 88% | 44,063 psi | 68% | 2595 fps | 95% |
| Rottweil R 905 | <<locked>> | 88% | 41,394 psi | 64% | 2595 fps | 95.8% |
| Rottweil R 907 | <<locked>> | 80% | 42,525 psi | 65% | 2539 fps | 97% |
| Shooters World Long Rifle | <<locked>> | 80% | 41,582 psi | 64% | 2523 fps | 98.4% |
| Shooters World Precision | <<locked>> | 80% | 50,212 psi | 77% | 2651 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 39,769 psi | 61% | 2503 fps | 97% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 46,746 psi | 72% | 2657 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 54,186 psi | 83% | 2736 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 55,259 psi | 85% | 2638 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 46,847 psi | 72% | 2513 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 40,553 psi | 62% | 2464 fps | 97.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 41,075 psi | 63% | 2592 fps | 95.7% |
| Somchem S335 | <<locked>> | 80% | 55,071 psi | 85% | 2635 fps | 100% |
| Somchem S355 | <<locked>> | 80% | 46,021 psi | 71% | 2608 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 48,211 psi | 74% | 2644 fps | 95.2% |
| Somchem S365 | <<locked>> | 80% | 34,983 psi | 54% | 2480 fps | 99.9% |
| Somchem S385 | <<locked>> | 84% | 36,869 psi | 57% | 2470 fps | 95.2% |
| Vihtavuori N135 | <<locked>> | 80% | 52,460 psi | 81% | 2625 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 52,460 psi | 81% | 2638 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 43,859 psi | 67% | 2536 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 39,755 psi | 61% | 2516 fps | 98.9% |
| Vihtavuori N165 | <<locked>> | 90% | 38,711 psi | 60% | 2503 fps | 95.4% |
| Vihtavuori N540 | <<locked>> | 80% | 50,691 psi | 78% | 2635 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 39,291 psi | 60% | 2520 fps | 98.7% |
| Vihtavuori N555 | <<locked>> | 80% | 30,618 psi | 47% | 2375 fps | 97.1% |
| Vihtavuori N560 | <<locked>> | 94% | 48,544 psi | 75% | 2789 fps | 95.7% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 38,754 psi | 60% | 2487 fps | 99.9% |
| Winchester 760 | <<locked>> | 80% | 40,828 psi | 63% | 2575 fps | 97.2% |
| Winchester StaBALL HD | <<locked>> | 80% | 24,381 psi | 38% | 2270 fps | 95.8% |
| Winchester StaBALL Match | <<locked>> | 80% | 54,447 psi | 84% | 2743 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 41,437 psi | 64% | 2566 fps | 95.6% |
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 105 powders for .280 Ackley Improved loaded with the .284 | 160gr | Sierra SBT GameKing. Alliant Reloder-26 delivers the highest muzzle velocity at 2,963 fps; across all powders the maximum-charge window runs from 1,719 fps to 2,963 fps. Accurate 3100 gives the best case fill at 100 %, and 105 of the 105 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (448 MPa), the top charges use 49–90 %, leaving at least 10 % headroom. The 160.0 gr projectile in 0.284" calls for a 1:11.5 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 .284 | 160gr | Sierra SBT GameKing they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, ADI AR 2217, Baschieri & Pellagri 109, Bofors RP30 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.