Load Specifications
Load data in caliber .280 Ackley Improved with .284 | 120gr | Prvi Partizan HP bullet and 97 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 60, ReloadSwiss RS 70 and Hodgdon Superformance.
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 2015 | <<locked>> | 84% | 58,305 psi | 90% | 3084 fps | 100% |
| Accurate 2495 | <<locked>> | 88% | 57,870 psi | 89% | 3114 fps | 100% |
| Accurate 2520 | <<locked>> | 82% | 55,492 psi | 85% | 3127 fps | 100% |
| Accurate 2700 | <<locked>> | 88% | 56,318 psi | 87% | 3104 fps | 96.8% |
| Accurate 3100ᴾ | <<locked>> | 100% | 45,208 psi | 70% | 2989 fps | 96.2% |
| Accurate 4064 | <<locked>> | 90% | 57,769 psi | 89% | 3159 fps | 100% |
| Accurate 4350 | <<locked>> | 98% | 58,494 psi | 90% | 3258 fps | 99.7% |
| ADI AR 2206H | <<locked>> | 86% | 57,566 psi | 89% | 3192 fps | 99.9% |
| ADI AR 2208 | <<locked>> | 92% | 58,697 psi | 90% | 3192 fps | 99.8% |
| ADI Benchmark 8208 | <<locked>> | 84% | 56,594 psi | 87% | 3143 fps | 100% |
| Alliant AR-Comp | <<locked>> | 84% | 57,725 psi | 89% | 3114 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 88% | 58,030 psi | 89% | 3330 fps | 99.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 90% | 55,405 psi | 85% | 3163 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 88% | 55,999 psi | 86% | 3186 fps | 99.8% |
| Alliant Reloder-16 | <<locked>> | 98% | 55,274 psi | 85% | 3255 fps | 99.7% |
| Alliant Reloder-17 | <<locked>> | 94% | 57,072 psi | 88% | 3297 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 42,699 psi | 66% | 3022 fps | 99% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 48,225 psi | 74% | 3202 fps | 98.5% |
| Baschieri & Pellagri 107 | <<locked>> | 86% | 57,769 psi | 89% | 3209 fps | 99.7% |
| Bofors RP3 | <<locked>> | 90% | 56,333 psi | 87% | 3179 fps | 100% |
| Bofors RP7 | <<locked>> | 94% | 56,086 psi | 86% | 3143 fps | 97% |
| Hodgdon Benchmark | <<locked>> | 84% | 57,856 psi | 89% | 3120 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 84% | 56,144 psi | 86% | 3169 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 82% | 58,479 psi | 90% | 3284 fps | 99.9% |
| Hodgdon H380 | <<locked>> | 90% | 57,145 psi | 88% | 3192 fps | 99.3% |
| Hodgdon H414 | <<locked>> | 96% | 57,203 psi | 88% | 3248 fps | 97.9% |
| Hodgdon H4350 | <<locked>> | 94% | 57,522 psi | 88% | 3209 fps | 96.6% |
| Hodgdon H4895 | <<locked>> | 86% | 58,189 psi | 90% | 3205 fps | 100% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 55,521 psi | 85% | 3179 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 88% | 58,262 psi | 90% | 3241 fps | 100% |
| Hodgdon Superformance | <<locked>> | 96% | 58,233 psi | 90% | 3291 fps | 97.7% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,737 psi | 55% | 1978 fps | 100% |
| Hodgdon VARGET | <<locked>> | 86% | 56,014 psi | 86% | 3153 fps | 100% |
| IMR 3031 | <<locked>> | 86% | 58,595 psi | 90% | 3189 fps | 100% |
| IMR 4064 | <<locked>> | 90% | 58,233 psi | 90% | 3176 fps | 99.9% |
| IMR 4166 Enduron | <<locked>> | 88% | 58,131 psi | 89% | 3156 fps | 97.9% |
| IMR 4350 | <<locked>> | 98% | 56,579 psi | 87% | 3173 fps | 97.2% |
| IMR 4451 Enduron | <<locked>> | 94% | 57,943 psi | 89% | 3179 fps | 97.8% |
| IMR 4831ᴾ | <<locked>> | 100% | 58,610 psi | 90% | 3238 fps | 99.7% |
| IMR 4895 | <<locked>> | 88% | 57,450 psi | 88% | 3219 fps | 100% |
| IMR 8208 XBR | <<locked>> | 84% | 56,594 psi | 87% | 3143 fps | 100% |
| Lovex D073.6 | <<locked>> | 86% | 57,943 psi | 89% | 3169 fps | 100% |
| Lovex S060 | <<locked>> | 86% | 56,681 psi | 87% | 3114 fps | 99.9% |
| Lovex S062 | <<locked>> | 90% | 58,102 psi | 89% | 3173 fps | 100% |
| Lovex S065 | <<locked>> | 96% | 57,667 psi | 89% | 3173 fps | 98.9% |
| Lovex S070 | <<locked>> | 98% | 58,798 psi | 90% | 3212 fps | 98.2% |
| Norma 201 | <<locked>> | 86% | 56,231 psi | 87% | 3136 fps | 100% |
| Norma 202 | <<locked>> | 86% | 56,840 psi | 87% | 3136 fps | 100% |
| Norma 203B | <<locked>> | 88% | 55,245 psi | 85% | 3173 fps | 99.9% |
| Norma 204 | <<locked>> | 98% | 57,624 psi | 89% | 3225 fps | 96.1% |
| Norma URP | <<locked>> | 98% | 57,014 psi | 88% | 3238 fps | 99.5% |
| Ramshot Big Game | <<locked>> | 88% | 56,144 psi | 86% | 3199 fps | 99.9% |
| Ramshot Hunter | <<locked>> | 98% | 55,825 psi | 86% | 3228 fps | 98.4% |
| Ramshot TAC | <<locked>> | 84% | 56,724 psi | 87% | 3156 fps | 98.9% |
| Ramshot Wild Boar | <<locked>> | 84% | 56,608 psi | 87% | 3179 fps | 99.9% |
| Ramshot X-Terminator | <<locked>> | 82% | 57,276 psi | 88% | 3140 fps | 99.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,230 psi | 56% | 2024 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 90% | 57,348 psi | 88% | 3173 fps | 98.3% |
| ReloadSwiss RS 52 | <<locked>> | 86% | 56,710 psi | 87% | 3258 fps | 99.8% |
| ReloadSwiss RS 60 | <<locked>> | 92% | 56,507 psi | 87% | 3294 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 58,349 psi | 90% | 3278 fps | 99.6% |
| ReloadSwiss RS 70 | <<locked>> | 98% | 57,537 psi | 89% | 3310 fps | 99.4% |
| Rottweil R 901 | <<locked>> | 84% | 57,188 psi | 88% | 3117 fps | 100% |
| Rottweil R 902 | <<locked>> | 88% | 56,942 psi | 88% | 3136 fps | 100% |
| Rottweil R 903 | <<locked>> | 92% | 56,202 psi | 86% | 3173 fps | 100% |
| Rottweil R 907 | <<locked>> | 94% | 56,086 psi | 86% | 3143 fps | 97% |
| Shooters World Long Rifle | <<locked>> | 96% | 57,667 psi | 89% | 3173 fps | 98.9% |
| Shooters World Match Rifle | <<locked>> | 86% | 57,943 psi | 89% | 3169 fps | 100% |
| Shooters World Precision | <<locked>> | 90% | 58,102 psi | 89% | 3173 fps | 100% |
| Shooters World SW4350 | <<locked>> | 98% | 58,798 psi | 90% | 3212 fps | 98.2% |
| SNPE Vectan SP 11 | <<locked>> | 92% | 58,204 psi | 90% | 3238 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 84% | 55,564 psi | 85% | 3136 fps | 99.1% |
| SNPE Vectan SP 9 | <<locked>> | 86% | 56,072 psi | 86% | 3159 fps | 99.9% |
| SNPE Vectan Tubal 3000 | <<locked>> | 86% | 57,450 psi | 88% | 3071 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 92% | 58,247 psi | 90% | 3068 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 96% | 57,827 psi | 89% | 3120 fps | 97.8% |
| Somchem S321 | <<locked>> | 82% | 58,044 psi | 89% | 3176 fps | 100% |
| Somchem S335 | <<locked>> | 86% | 56,956 psi | 88% | 3064 fps | 100% |
| Somchem S341 | <<locked>> | 84% | 54,940 psi | 85% | 3123 fps | 99.8% |
| Somchem S355 | <<locked>> | 92% | 56,434 psi | 87% | 3169 fps | 100% |
| Somchem S365ᴾ | <<locked>> | 100% | 55,361 psi | 85% | 3241 fps | 100% |
| Somchem S385ᴾ | <<locked>> | 100% | 51,140 psi | 79% | 3104 fps | 96% |
| Vihtavuori N130 | <<locked>> | 82% | 56,985 psi | 88% | 3028 fps | 100% |
| Vihtavuori N133 | <<locked>> | 86% | 57,711 psi | 89% | 3051 fps | 100% |
| Vihtavuori N135 | <<locked>> | 88% | 56,927 psi | 88% | 3097 fps | 100% |
| Vihtavuori N140 | <<locked>> | 88% | 57,580 psi | 89% | 3114 fps | 100% |
| Vihtavuori N150 | <<locked>> | 94% | 58,030 psi | 89% | 3146 fps | 100% |
| Vihtavuori N160 | <<locked>> | 96% | 55,811 psi | 86% | 3176 fps | 99.4% |
| Vihtavuori N530 | <<locked>> | 84% | 56,913 psi | 88% | 3140 fps | 100% |
| Vihtavuori N540 | <<locked>> | 88% | 55,724 psi | 86% | 3107 fps | 100% |
| Vihtavuori N550 | <<locked>> | 98% | 58,566 psi | 90% | 3238 fps | 99.5% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 47,253 psi | 73% | 3107 fps | 98.9% |
| Winchester 6.5 StaBALL | <<locked>> | 96% | 56,202 psi | 86% | 3153 fps | 100% |
| Winchester 748 | <<locked>> | 84% | 57,464 psi | 88% | 3192 fps | 100% |
| Winchester 760 | <<locked>> | 96% | 57,508 psi | 88% | 3251 fps | 97.9% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 38,261 psi | 59% | 3022 fps | 99% |
| Winchester StaBALL Match | <<locked>> | 86% | 56,202 psi | 86% | 3169 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% | 51,576 psi | 79% | 2986 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 44,483 psi | 68% | 2900 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 51,953 psi | 80% | 3071 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 49,530 psi | 76% | 2986 fps | 95.3% |
| Accurate 3100 | <<locked>> | 98% | 42,105 psi | 65% | 2927 fps | 95.3% |
| Accurate 4064 | <<locked>> | 80% | 42,076 psi | 65% | 2894 fps | 100% |
| Accurate 4350 | <<locked>> | 84% | 35,926 psi | 55% | 2812 fps | 95.1% |
| ADI AR 2206H | <<locked>> | 80% | 47,659 psi | 73% | 3018 fps | 99.2% |
| ADI AR 2208 | <<locked>> | 80% | 40,480 psi | 62% | 2848 fps | 97.3% |
| ADI Benchmark 8208 | <<locked>> | 80% | 49,734 psi | 77% | 3028 fps | 99.9% |
| Alliant AR-Comp | <<locked>> | 80% | 50,459 psi | 78% | 3012 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 43,685 psi | 67% | 3051 fps | 98% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 40,437 psi | 62% | 2874 fps | 98.6% |
| Alliant Reloder-15 | <<locked>> | 80% | 43,294 psi | 67% | 2946 fps | 98.1% |
| Alliant Reloder-16 | <<locked>> | 84% | 35,650 psi | 55% | 2825 fps | 95.1% |
| Alliant Reloder-17 | <<locked>> | 80% | 35,070 psi | 54% | 2835 fps | 96.8% |
| Alliant Reloder-23 | <<locked>> | 92% | 33,083 psi | 51% | 2772 fps | 95.9% |
| Alliant Reloder-26 | <<locked>> | 94% | 38,798 psi | 60% | 2982 fps | 95.6% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 47,195 psi | 73% | 3022 fps | 98.4% |
| Bofors RP3 | <<locked>> | 80% | 40,393 psi | 62% | 2881 fps | 98.7% |
| Bofors RP7 | <<locked>> | 90% | 49,472 psi | 76% | 3025 fps | 95.6% |
| Hodgdon Benchmark | <<locked>> | 80% | 51,184 psi | 79% | 3012 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 80% | 49,037 psi | 75% | 3048 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 80% | 54,389 psi | 84% | 3215 fps | 99.6% |
| Hodgdon H380 | <<locked>> | 80% | 40,959 psi | 63% | 2881 fps | 96.3% |
| Hodgdon H414 | <<locked>> | 90% | 46,833 psi | 72% | 3058 fps | 95.6% |
| Hodgdon H4350 | <<locked>> | 90% | 50,488 psi | 78% | 3084 fps | 95% |
| Hodgdon H4895 | <<locked>> | 80% | 48,124 psi | 74% | 3031 fps | 99.5% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 30,763 psi | 47% | 2651 fps | 95% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 44,425 psi | 68% | 2999 fps | 99.4% |
| Hodgdon Superformance | 63.6 gr | 90% | 46,630 psi | 72% | 3074 fps | 95% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,614 psi | 41% | 1772 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 46,021 psi | 71% | 2976 fps | 99.3% |
| IMR 3031 | <<locked>> | 80% | 48,138 psi | 74% | 3025 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 42,525 psi | 65% | 2890 fps | 98% |
| IMR 4166 Enduron | <<locked>> | 80% | 44,962 psi | 69% | 2910 fps | 95% |
| IMR 4350 | <<locked>> | 94% | 49,966 psi | 77% | 3054 fps | 95.8% |
| IMR 4451 Enduron | <<locked>> | 86% | 45,353 psi | 70% | 2943 fps | 95% |
| IMR 4831 | <<locked>> | 86% | 37,028 psi | 57% | 2822 fps | 95.7% |
| IMR 4895 | <<locked>> | 80% | 44,367 psi | 68% | 2979 fps | 98.8% |
| IMR 8208 XBR | <<locked>> | 80% | 49,734 psi | 77% | 3028 fps | 99.9% |
| Lovex D073.6 | <<locked>> | 80% | 47,369 psi | 73% | 2999 fps | 100% |
| Lovex S060 | <<locked>> | 80% | 47,239 psi | 73% | 2946 fps | 99.2% |
| Lovex S062 | <<locked>> | 80% | 42,525 psi | 65% | 2894 fps | 99.3% |
| Lovex S065 | <<locked>> | 86% | 42,192 psi | 65% | 2881 fps | 95.7% |
| Lovex S070 | <<locked>> | 90% | 45,803 psi | 70% | 2976 fps | 95.5% |
| Norma 201 | <<locked>> | 80% | 46,659 psi | 72% | 2966 fps | 99.7% |
| Norma 202 | <<locked>> | 80% | 47,137 psi | 73% | 2976 fps | 100% |
| Norma 203B | <<locked>> | 80% | 42,656 psi | 66% | 2930 fps | 98.4% |
| Norma 204 | <<locked>> | 96% | 53,824 psi | 83% | 3163 fps | 95.2% |
| Norma URP | <<locked>> | 84% | 35,984 psi | 55% | 2812 fps | 95% |
| Ramshot Big Game | <<locked>> | 80% | 42,424 psi | 65% | 2943 fps | 98.2% |
| Ramshot Hunter | <<locked>> | 90% | 42,873 psi | 66% | 2979 fps | 95.4% |
| Ramshot TAC | <<locked>> | 80% | 49,821 psi | 77% | 3031 fps | 97.8% |
| Ramshot Wild Boar | <<locked>> | 80% | 49,516 psi | 76% | 3054 fps | 99.4% |
| Ramshot X-Terminator | <<locked>> | 80% | 53,563 psi | 82% | 3077 fps | 99.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,934 psi | 41% | 1811 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 44,150 psi | 68% | 2923 fps | 95.5% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 46,108 psi | 71% | 3064 fps | 98.6% |
| ReloadSwiss RS 60 | 53.5 gr | 80% | 37,289 psi | 57% | 2910 fps | 99.5% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 38,261 psi | 59% | 2890 fps | 95.6% |
| ReloadSwiss RS 70 | 59.8 gr | 88% | 40,654 psi | 63% | 2966 fps | 95.8% |
| Rottweil R 901 | <<locked>> | 80% | 50,778 psi | 78% | 3015 fps | 100% |
| Rottweil R 902 | <<locked>> | 80% | 44,440 psi | 68% | 2913 fps | 99.5% |
| Rottweil R 903 | <<locked>> | 80% | 37,782 psi | 58% | 2815 fps | 97.9% |
| Rottweil R 907 | <<locked>> | 90% | 49,472 psi | 76% | 3025 fps | 95.6% |
| Shooters World Long Rifle | <<locked>> | 86% | 42,192 psi | 65% | 2881 fps | 95.7% |
| Shooters World Match Rifle | <<locked>> | 80% | 47,369 psi | 73% | 2999 fps | 100% |
| Shooters World Precision | <<locked>> | 80% | 42,525 psi | 65% | 2894 fps | 99.3% |
| Shooters World SW4350 | <<locked>> | 90% | 45,803 psi | 70% | 2976 fps | 95.5% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 38,957 psi | 60% | 2871 fps | 97.4% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 48,225 psi | 74% | 3005 fps | 97.9% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 46,267 psi | 71% | 2986 fps | 99% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 47,688 psi | 73% | 2913 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 39,900 psi | 61% | 2762 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 90% | 47,601 psi | 73% | 2943 fps | 95.8% |
| Somchem S321 | <<locked>> | 80% | 54,201 psi | 83% | 3117 fps | 100% |
| Somchem S335 | <<locked>> | 80% | 47,529 psi | 73% | 2913 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 48,037 psi | 74% | 3002 fps | 99.2% |
| Somchem S355 | <<locked>> | 80% | 38,566 psi | 59% | 2825 fps | 97.9% |
| Somchem S365 | <<locked>> | 80% | 28,137 psi | 43% | 2625 fps | 95.2% |
| Somchem S385 | <<locked>> | 98% | 48,080 psi | 74% | 3045 fps | 95.2% |
| Vihtavuori N130 | <<locked>> | 80% | 53,664 psi | 83% | 2979 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 48,095 psi | 74% | 2904 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 44,048 psi | 68% | 2894 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 44,483 psi | 68% | 2897 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 36,622 psi | 56% | 2749 fps | 98.6% |
| Vihtavuori N160 | <<locked>> | 84% | 37,579 psi | 58% | 2818 fps | 95.6% |
| Vihtavuori N530 | <<locked>> | 80% | 50,082 psi | 77% | 3025 fps | 99.9% |
| Vihtavuori N540 | <<locked>> | 80% | 43,047 psi | 66% | 2887 fps | 100% |
| Vihtavuori N550 | <<locked>> | 84% | 36,941 psi | 57% | 2812 fps | 95.1% |
| Vihtavuori N555 | <<locked>> | 90% | 33,852 psi | 52% | 2799 fps | 95.1% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 32,561 psi | 50% | 2664 fps | 96.1% |
| Winchester 748 | <<locked>> | 80% | 50,096 psi | 77% | 3074 fps | 100% |
| Winchester 760 | <<locked>> | 90% | 46,833 psi | 72% | 3058 fps | 95.6% |
| Winchester StaBALL HD | <<locked>> | 94% | 31,459 psi | 48% | 2802 fps | 95.6% |
| Winchester StaBALL Match | <<locked>> | 80% | 45,948 psi | 71% | 2989 fps | 99.3% |
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 .284 | 120gr | Prvi Partizan HP. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,330 fps; across all powders the maximum-charge window runs from 1,978 fps to 3,330 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 55–90 %, leaving at least 10 % headroom. The 120.0 gr projectile in 0.284" calls for a 1:13.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, Alliant Reloder-23, Alliant Reloder-26 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, ReloadSwiss RS 70, Hodgdon Superformance rank at the top here: for .280 Ackley Improved with the .284 | 120gr | Prvi Partizan HP 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.