Load Specifications
Load data in caliber .260 Ackley Improved with .264 | 120gr | Speer Spitzer Soft Point 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-17, ReloadSwiss RS 60 and Winchester 760.
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>> | 84% | 56,304 psi | 90% | 2802 fps | 100% |
| Accurate 2495 | <<locked>> | 88% | 55,201 psi | 89% | 2825 fps | 100% |
| Accurate 2520 | <<locked>> | 82% | 52,924 psi | 85% | 2838 fps | 100% |
| Accurate 2700 | <<locked>> | 88% | 54,157 psi | 87% | 2822 fps | 96.9% |
| Accurate 3100ᴾ | <<locked>> | 100% | 42,090 psi | 67% | 2713 fps | 96.1% |
| Accurate 4064 | <<locked>> | 90% | 55,129 psi | 88% | 2874 fps | 100% |
| Accurate 4350 | <<locked>> | 98% | 55,071 psi | 88% | 2959 fps | 99.6% |
| ADI AR 2206H | <<locked>> | 86% | 55,216 psi | 89% | 2900 fps | 100% |
| ADI AR 2208 | <<locked>> | 92% | 56,391 psi | 90% | 2904 fps | 99.9% |
| ADI Benchmark 8208 | <<locked>> | 84% | 54,331 psi | 87% | 2854 fps | 100% |
| Alliant AR-Comp | <<locked>> | 84% | 55,245 psi | 89% | 2828 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 88% | 55,143 psi | 88% | 3025 fps | 99.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 92% | 56,289 psi | 90% | 2923 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 88% | 53,679 psi | 86% | 2897 fps | 99.8% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 56,043 psi | 90% | 3012 fps | 99.9% |
| Alliant Reloder-17 | <<locked>> | 94% | 53,867 psi | 86% | 2999 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 40,190 psi | 64% | 2746 fps | 98.9% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 44,904 psi | 72% | 2907 fps | 98.3% |
| Baschieri & Pellagri 107 | <<locked>> | 86% | 55,158 psi | 88% | 2917 fps | 99.7% |
| Bofors RP3 | <<locked>> | 90% | 53,679 psi | 86% | 2890 fps | 100% |
| Bofors RP7 | <<locked>> | 94% | 53,795 psi | 86% | 2858 fps | 97.1% |
| Hodgdon Benchmark | <<locked>> | 84% | 55,985 psi | 90% | 2835 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 84% | 53,824 psi | 86% | 2884 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 82% | 55,564 psi | 89% | 2982 fps | 99.9% |
| Hodgdon H380 | <<locked>> | 90% | 54,389 psi | 87% | 2900 fps | 99.3% |
| Hodgdon H414 | <<locked>> | 96% | 54,114 psi | 87% | 2953 fps | 97.8% |
| Hodgdon H4350 | <<locked>> | 94% | 54,882 psi | 88% | 2917 fps | 96.6% |
| Hodgdon H4895 | <<locked>> | 86% | 55,767 psi | 89% | 2913 fps | 100% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 52,388 psi | 84% | 2887 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 88% | 55,390 psi | 89% | 2946 fps | 100% |
| Hodgdon Superformance | <<locked>> | 96% | 54,563 psi | 87% | 2986 fps | 97.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,462 psi | 57% | 1772 fps | 100% |
| Hodgdon VARGET | <<locked>> | 86% | 53,621 psi | 86% | 2864 fps | 100% |
| IMR 3031 | <<locked>> | 86% | 56,101 psi | 90% | 2897 fps | 100% |
| IMR 4064 | <<locked>> | 90% | 55,985 psi | 90% | 2887 fps | 99.9% |
| IMR 4166 Enduron | <<locked>> | 88% | 55,854 psi | 90% | 2867 fps | 97.9% |
| IMR 4350 | <<locked>> | 98% | 53,867 psi | 86% | 2881 fps | 97.1% |
| IMR 4451 Enduron | <<locked>> | 94% | 55,666 psi | 89% | 2890 fps | 97.8% |
| IMR 4831ᴾ | <<locked>> | 100% | 55,434 psi | 89% | 2946 fps | 99.7% |
| IMR 4895 | <<locked>> | 88% | 55,056 psi | 88% | 2927 fps | 100% |
| IMR 8208 XBR | <<locked>> | 84% | 54,331 psi | 87% | 2854 fps | 100% |
| Lovex D073.6 | <<locked>> | 86% | 55,332 psi | 89% | 2881 fps | 100% |
| Lovex S060 | <<locked>> | 86% | 54,665 psi | 88% | 2828 fps | 99.9% |
| Lovex S062 | <<locked>> | 90% | 55,825 psi | 90% | 2884 fps | 100% |
| Lovex S065 | <<locked>> | 96% | 55,143 psi | 88% | 2887 fps | 98.9% |
| Lovex S070 | <<locked>> | 98% | 55,999 psi | 90% | 2920 fps | 98.2% |
| Norma 201 | <<locked>> | 86% | 54,288 psi | 87% | 2851 fps | 100% |
| Norma 202 | <<locked>> | 86% | 54,708 psi | 88% | 2851 fps | 100% |
| Norma 203B | <<locked>> | 90% | 56,202 psi | 90% | 2933 fps | 100% |
| Norma 204 | <<locked>> | 98% | 54,650 psi | 88% | 2933 fps | 96% |
| Norma URP | <<locked>> | 98% | 54,012 psi | 87% | 2943 fps | 99.5% |
| Ramshot Big Game | <<locked>> | 88% | 53,345 psi | 86% | 2907 fps | 99.9% |
| Ramshot Hunterᴾ | <<locked>> | 100% | 56,144 psi | 90% | 2992 fps | 98.8% |
| Ramshot TAC | <<locked>> | 84% | 54,592 psi | 88% | 2871 fps | 98.9% |
| Ramshot Wild Boar | <<locked>> | 84% | 54,172 psi | 87% | 2890 fps | 99.9% |
| Ramshot X-Terminator | <<locked>> | 82% | 55,274 psi | 89% | 2858 fps | 99.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,940 psi | 58% | 1811 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 90% | 54,723 psi | 88% | 2881 fps | 98.3% |
| ReloadSwiss RS 52 | <<locked>> | 86% | 54,157 psi | 87% | 2963 fps | 99.8% |
| ReloadSwiss RS 60 | <<locked>> | 92% | 53,577 psi | 86% | 2995 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 54,694 psi | 88% | 2979 fps | 99.5% |
| ReloadSwiss RS 70 | <<locked>> | 98% | 54,259 psi | 87% | 3009 fps | 99.3% |
| Rottweil R 901 | <<locked>> | 84% | 55,027 psi | 88% | 2828 fps | 100% |
| Rottweil R 902 | <<locked>> | 88% | 54,708 psi | 88% | 2848 fps | 100% |
| Rottweil R 903 | <<locked>> | 92% | 53,563 psi | 86% | 2884 fps | 100% |
| Rottweil R 907 | <<locked>> | 94% | 53,795 psi | 86% | 2858 fps | 97.1% |
| Shooters World Long Rifle | <<locked>> | 96% | 55,143 psi | 88% | 2887 fps | 98.9% |
| Shooters World Match Rifle | <<locked>> | 86% | 55,332 psi | 89% | 2881 fps | 100% |
| Shooters World Precision | <<locked>> | 90% | 55,825 psi | 90% | 2884 fps | 100% |
| Shooters World SW4350 | <<locked>> | 98% | 55,999 psi | 90% | 2920 fps | 98.2% |
| SNPE Vectan SP 11 | <<locked>> | 92% | 55,332 psi | 89% | 2943 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 84% | 53,084 psi | 85% | 2851 fps | 99.1% |
| SNPE Vectan SP 9 | <<locked>> | 86% | 53,911 psi | 86% | 2877 fps | 99.9% |
| SNPE Vectan Tubal 3000 | <<locked>> | 86% | 55,419 psi | 89% | 2785 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 92% | 55,811 psi | 89% | 2782 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 96% | 55,201 psi | 89% | 2835 fps | 97.8% |
| Somchem S321 | <<locked>> | 82% | 55,550 psi | 89% | 2884 fps | 100% |
| Somchem S335 | <<locked>> | 86% | 55,071 psi | 88% | 2785 fps | 100% |
| Somchem S341 | <<locked>> | 86% | 56,217 psi | 90% | 2894 fps | 100% |
| Somchem S355 | <<locked>> | 92% | 53,737 psi | 86% | 2877 fps | 100% |
| Somchem S365ᴾ | <<locked>> | 100% | 52,069 psi | 83% | 2946 fps | 100% |
| Somchem S385ᴾ | <<locked>> | 100% | 48,167 psi | 77% | 2822 fps | 95.9% |
| Vihtavuori N130 | <<locked>> | 82% | 55,405 psi | 89% | 2749 fps | 100% |
| Vihtavuori N133 | <<locked>> | 86% | 55,651 psi | 89% | 2769 fps | 100% |
| Vihtavuori N135 | <<locked>> | 88% | 54,302 psi | 87% | 2812 fps | 100% |
| Vihtavuori N140 | <<locked>> | 88% | 55,071 psi | 88% | 2825 fps | 100% |
| Vihtavuori N150 | <<locked>> | 94% | 55,143 psi | 88% | 2858 fps | 100% |
| Vihtavuori N160 | <<locked>> | 96% | 52,765 psi | 85% | 2884 fps | 99.3% |
| Vihtavuori N530 | <<locked>> | 84% | 54,665 psi | 88% | 2851 fps | 100% |
| Vihtavuori N540 | <<locked>> | 88% | 53,447 psi | 86% | 2825 fps | 100% |
| Vihtavuori N550 | <<locked>> | 98% | 55,593 psi | 89% | 2946 fps | 99.5% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 44,222 psi | 71% | 2825 fps | 98.8% |
| Winchester 6.5 StaBALL | <<locked>> | 96% | 53,200 psi | 85% | 2867 fps | 100% |
| Winchester 748 | <<locked>> | 84% | 54,607 psi | 88% | 2900 fps | 100% |
| Winchester 760 | <<locked>> | 96% | 54,462 psi | 87% | 2956 fps | 97.9% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 35,882 psi | 58% | 2743 fps | 98.8% |
| Winchester StaBALL Match | <<locked>> | 86% | 53,534 psi | 86% | 2881 fps | 100% |
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% | 49,777 psi | 80% | 2707 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 42,496 psi | 68% | 2635 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 49,719 psi | 80% | 2789 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 47,413 psi | 76% | 2710 fps | 95.4% |
| Accurate 3100 | <<locked>> | 98% | 39,349 psi | 63% | 2657 fps | 95.2% |
| Accurate 4064 | <<locked>> | 80% | 40,205 psi | 64% | 2628 fps | 100% |
| Accurate 4350 | <<locked>> | 84% | 33,866 psi | 54% | 2556 fps | 95.3% |
| ADI AR 2206H | <<locked>> | 80% | 45,788 psi | 73% | 2743 fps | 99.3% |
| ADI AR 2208 | <<locked>> | 80% | 38,943 psi | 62% | 2589 fps | 97.5% |
| ADI Benchmark 8208 | <<locked>> | 80% | 47,848 psi | 77% | 2749 fps | 99.9% |
| Alliant AR-Comp | <<locked>> | 80% | 48,501 psi | 78% | 2736 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 41,887 psi | 67% | 2779 fps | 98.2% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 38,682 psi | 62% | 2615 fps | 98.8% |
| Alliant Reloder-15 | <<locked>> | 80% | 41,495 psi | 67% | 2677 fps | 98.2% |
| Alliant Reloder-16 | <<locked>> | 84% | 34,142 psi | 55% | 2569 fps | 95.4% |
| Alliant Reloder-17 | 39.5 gr | 80% | 33,547 psi | 54% | 2582 fps | 97.1% |
| Alliant Reloder-23 | <<locked>> | 90% | 29,530 psi | 47% | 2467 fps | 95% |
| Alliant Reloder-26 | <<locked>> | 94% | 36,434 psi | 58% | 2713 fps | 95.5% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 45,165 psi | 72% | 2749 fps | 98.5% |
| Bofors RP3 | <<locked>> | 80% | 38,363 psi | 62% | 2618 fps | 98.8% |
| Bofors RP7 | <<locked>> | 90% | 47,311 psi | 76% | 2749 fps | 95.6% |
| Hodgdon Benchmark | <<locked>> | 80% | 49,429 psi | 79% | 2736 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 80% | 47,036 psi | 75% | 2776 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 80% | 51,837 psi | 83% | 2920 fps | 99.7% |
| Hodgdon H380 | <<locked>> | 80% | 39,117 psi | 63% | 2618 fps | 96.4% |
| Hodgdon H414 | <<locked>> | 90% | 44,280 psi | 71% | 2776 fps | 95.6% |
| Hodgdon H4350 | <<locked>> | 90% | 48,298 psi | 77% | 2802 fps | 95.1% |
| Hodgdon H4895 | <<locked>> | 80% | 46,195 psi | 74% | 2753 fps | 99.6% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 29,399 psi | 47% | 2411 fps | 95.3% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 42,366 psi | 68% | 2726 fps | 99.5% |
| Hodgdon Superformance | <<locked>> | 92% | 47,572 psi | 76% | 2861 fps | 95.9% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,585 psi | 43% | 1585 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 44,382 psi | 71% | 2707 fps | 99.4% |
| IMR 3031 | <<locked>> | 80% | 45,905 psi | 74% | 2746 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 40,901 psi | 66% | 2625 fps | 98.2% |
| IMR 4166 Enduron | <<locked>> | 80% | 43,453 psi | 70% | 2648 fps | 95.2% |
| IMR 4350 | <<locked>> | 94% | 47,805 psi | 77% | 2779 fps | 95.8% |
| IMR 4451 Enduron | <<locked>> | 86% | 43,352 psi | 70% | 2671 fps | 95.1% |
| IMR 4831 | <<locked>> | 86% | 35,157 psi | 56% | 2569 fps | 95.9% |
| IMR 4895 | <<locked>> | 80% | 42,467 psi | 68% | 2707 fps | 98.9% |
| IMR 8208 XBR | <<locked>> | 80% | 47,848 psi | 77% | 2749 fps | 99.9% |
| Lovex D073.6 | <<locked>> | 80% | 45,295 psi | 73% | 2726 fps | 100% |
| Lovex S060 | <<locked>> | 80% | 45,730 psi | 73% | 2680 fps | 99.3% |
| Lovex S062 | <<locked>> | 80% | 40,901 psi | 66% | 2628 fps | 99.4% |
| Lovex S065 | <<locked>> | 84% | 37,971 psi | 61% | 2569 fps | 95.1% |
| Lovex S070 | <<locked>> | 90% | 43,743 psi | 70% | 2707 fps | 95.6% |
| Norma 201 | <<locked>> | 80% | 44,904 psi | 72% | 2694 fps | 99.8% |
| Norma 202 | <<locked>> | 80% | 45,252 psi | 73% | 2703 fps | 100% |
| Norma 203B | <<locked>> | 80% | 40,872 psi | 66% | 2664 fps | 98.6% |
| Norma 204 | <<locked>> | 96% | 50,981 psi | 82% | 2871 fps | 95.1% |
| Norma URP | <<locked>> | 84% | 34,229 psi | 55% | 2559 fps | 95.2% |
| Ramshot Big Game | <<locked>> | 80% | 40,582 psi | 65% | 2680 fps | 98.4% |
| Ramshot Hunter | <<locked>> | 90% | 40,596 psi | 65% | 2707 fps | 95.4% |
| Ramshot TAC | <<locked>> | 80% | 47,950 psi | 77% | 2759 fps | 97.9% |
| Ramshot Wild Boar | <<locked>> | 80% | 47,456 psi | 76% | 2779 fps | 99.5% |
| Ramshot X-Terminator | <<locked>> | 80% | 51,459 psi | 83% | 2799 fps | 99.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,818 psi | 43% | 1621 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 42,221 psi | 68% | 2657 fps | 95.6% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 43,743 psi | 70% | 2782 fps | 98.7% |
| ReloadSwiss RS 60 | 39.5 gr | 80% | 35,679 psi | 57% | 2651 fps | 99.6% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 36,071 psi | 58% | 2628 fps | 95.7% |
| ReloadSwiss RS 70 | <<locked>> | 88% | 38,624 psi | 62% | 2697 fps | 95.7% |
| Rottweil R 901 | <<locked>> | 80% | 48,820 psi | 78% | 2733 fps | 100% |
| Rottweil R 902 | <<locked>> | 80% | 42,859 psi | 69% | 2648 fps | 99.6% |
| Rottweil R 903 | <<locked>> | 80% | 36,129 psi | 58% | 2562 fps | 98.1% |
| Rottweil R 907 | <<locked>> | 90% | 47,311 psi | 76% | 2749 fps | 95.6% |
| Shooters World Long Rifle | <<locked>> | 84% | 37,971 psi | 61% | 2569 fps | 95.1% |
| Shooters World Match Rifle | <<locked>> | 80% | 45,295 psi | 73% | 2726 fps | 100% |
| Shooters World Precision | <<locked>> | 80% | 40,901 psi | 66% | 2628 fps | 99.4% |
| Shooters World SW4350 | <<locked>> | 90% | 43,743 psi | 70% | 2707 fps | 95.6% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 36,970 psi | 59% | 2608 fps | 97.5% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 46,354 psi | 74% | 2736 fps | 98.1% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 44,193 psi | 71% | 2710 fps | 99.1% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 46,267 psi | 74% | 2648 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 38,580 psi | 62% | 2513 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 88% | 42,699 psi | 68% | 2621 fps | 95.1% |
| Somchem S321 | <<locked>> | 80% | 51,996 psi | 83% | 2831 fps | 100% |
| Somchem S335 | <<locked>> | 80% | 45,847 psi | 74% | 2648 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 46,021 psi | 74% | 2730 fps | 99.3% |
| Somchem S355 | <<locked>> | 80% | 36,956 psi | 59% | 2569 fps | 98.1% |
| Somchem S365 | <<locked>> | 80% | 26,861 psi | 43% | 2392 fps | 95.6% |
| Somchem S385 | <<locked>> | 98% | 45,266 psi | 73% | 2766 fps | 95.1% |
| Vihtavuori N130 | <<locked>> | 80% | 52,127 psi | 84% | 2703 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 46,615 psi | 75% | 2638 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 42,380 psi | 68% | 2628 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 42,815 psi | 69% | 2635 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 35,143 psi | 56% | 2503 fps | 98.8% |
| Vihtavuori N160 | <<locked>> | 84% | 35,694 psi | 57% | 2559 fps | 95.7% |
| Vihtavuori N530 | <<locked>> | 80% | 47,979 psi | 77% | 2746 fps | 99.9% |
| Vihtavuori N540 | <<locked>> | 80% | 41,205 psi | 66% | 2621 fps | 100% |
| Vihtavuori N550 | <<locked>> | 84% | 35,230 psi | 56% | 2562 fps | 95.3% |
| Vihtavuori N555 | <<locked>> | 90% | 31,807 psi | 51% | 2546 fps | 95.2% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 31,183 psi | 50% | 2428 fps | 96.3% |
| Winchester 748 | <<locked>> | 80% | 47,935 psi | 77% | 2795 fps | 100% |
| Winchester 760 | 43.5 gr | 90% | 44,585 psi | 71% | 2782 fps | 95.7% |
| Winchester StaBALL HD | <<locked>> | 94% | 29,602 psi | 47% | 2546 fps | 95.5% |
| Winchester StaBALL Match | <<locked>> | 80% | 44,019 psi | 71% | 2720 fps | 99.4% |
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 .260 Ackley Improved loaded with the .264 | 120gr | Speer Spitzer Soft Point. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,025 fps; across all powders the maximum-charge window runs from 1,772 fps to 3,025 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 (430 MPa), the top charges use 57–90 %, leaving at least 10 % headroom. The 120.0 gr projectile in 0.264" calls for a 1:11.5 twist; slower twists will usually not stabilise this weight. Accurate 3100, Alliant Reloder-16, Alliant Reloder-23 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 60, Winchester 760 rank at the top here: for .260 Ackley Improved with the .264 | 120gr | Speer Spitzer Soft Point 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.