Load Specifications
Load data in caliber 7.21 Firebird with .284 | 175gr | Sierra MatchKing bullet and 45 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2218, Vihtavuori N570 and Alliant Reloder-33.
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: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 82% | 58,305 psi | 87% | 2894 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 60,147 psi | 90% | 3041 fps | 99.8% |
| ADI AR 2213 | <<locked>> | 82% | 58,160 psi | 87% | 3009 fps | 100% |
| ADI AR 2217 | <<locked>> | 90% | 58,552 psi | 88% | 3002 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 59,944 psi | 90% | 3159 fps | 100% |
| ADI AR 2225 | <<locked>> | 92% | 58,987 psi | 88% | 3025 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 58,755 psi | 88% | 2999 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 82% | 57,246 psi | 86% | 2894 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 86% | 58,711 psi | 88% | 2982 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 90% | 57,754 psi | 87% | 3061 fps | 99.8% |
| Alliant Reloder-50 | <<locked>> | 94% | 58,523 psi | 88% | 3064 fps | 99.7% |
| Baschieri & Pellagri 109 | <<locked>> | 84% | 57,914 psi | 87% | 2972 fps | 99.8% |
| Bofors RP15 | <<locked>> | 84% | 58,349 psi | 87% | 2995 fps | 100% |
| Bofors RP30 | <<locked>> | 88% | 58,653 psi | 88% | 3018 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 58,755 psi | 88% | 2999 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 59,988 psi | 90% | 3018 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 60,278 psi | 90% | 2995 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 59,117 psi | 89% | 2976 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 86% | 59,045 psi | 89% | 3084 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,348 psi | 57% | 1919 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 56,260 psi | 84% | 2979 fps | 96.5% |
| IMR 4955 Enduron | <<locked>> | 82% | 59,770 psi | 90% | 2966 fps | 100% |
| IMR 7828 SSC | <<locked>> | 82% | 57,101 psi | 86% | 2999 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 58,537 psi | 88% | 2936 fps | 98.1% |
| IMR 8133 Enduron | <<locked>> | 94% | 57,885 psi | 87% | 3022 fps | 100% |
| Lovex D100 | <<locked>> | 90% | 56,710 psi | 85% | 2933 fps | 97% |
| Lovex S071 | <<locked>> | 86% | 57,000 psi | 85% | 2874 fps | 100% |
| Norma 217 | <<locked>> | 94% | 59,756 psi | 90% | 3038 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 58,871 psi | 88% | 3022 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 59,001 psi | 88% | 3081 fps | 97.2% |
| Ramshot Magnum | <<locked>> | 84% | 57,174 psi | 86% | 2943 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,378 psi | 59% | 1962 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 60,060 psi | 90% | 3071 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 58,755 psi | 88% | 3051 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 56,710 psi | 85% | 2933 fps | 97% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 57,217 psi | 86% | 2979 fps | 99.4% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 54,679 psi | 82% | 2959 fps | 98% |
| Vihtavuori 24N41 | <<locked>> | 94% | 56,724 psi | 85% | 2989 fps | 96.5% |
| Vihtavuori N165 | <<locked>> | 84% | 58,871 psi | 88% | 2920 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 58,610 psi | 88% | 2976 fps | 99.2% |
| Vihtavuori N565 | <<locked>> | 86% | 60,205 psi | 90% | 3028 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 58,827 psi | 88% | 3054 fps | 100% |
| Vihtavuori N570 | <<locked>> | 88% | 56,623 psi | 85% | 3064 fps | 99.6% |
| Winchester StaBALL HD | <<locked>> | 82% | 59,582 psi | 89% | 2992 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 58,421 psi | 88% | 2930 fps | 100% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 80% | 54,636 psi | 82% | 2841 fps | 100% |
| Accurate 8700 | <<locked>> | 88% | 38,682 psi | 58% | 2654 fps | 95.6% |
| ADI AR 2213 | <<locked>> | 80% | 54,375 psi | 82% | 2949 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 41,220 psi | 62% | 2710 fps | 99.6% |
| ADI AR 2218 | 88.3 gr | 82% | 38,189 psi | 57% | 2726 fps | 96% |
| ADI AR 2225 | <<locked>> | 80% | 38,624 psi | 58% | 2684 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 55,056 psi | 83% | 2943 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 53,592 psi | 80% | 2844 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 47,993 psi | 72% | 2822 fps | 100% |
| Alliant Reloder-33 | 87.7 gr | 80% | 39,784 psi | 60% | 2720 fps | 96.4% |
| Alliant Reloder-50 | <<locked>> | 82% | 37,666 psi | 56% | 2657 fps | 95% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 50,792 psi | 76% | 2858 fps | 99.2% |
| Bofors RP15 | <<locked>> | 80% | 51,242 psi | 77% | 2881 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 44,788 psi | 67% | 2785 fps | 99.9% |
| Bofors RP5 | <<locked>> | 80% | 55,056 psi | 83% | 2943 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 45,049 psi | 68% | 2782 fps | 100% |
| Hodgdon H4831 | <<locked>> | 80% | 56,260 psi | 84% | 2936 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 80% | 55,361 psi | 83% | 2920 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 47,630 psi | 71% | 2907 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,892 psi | 43% | 1719 fps | 100% |
| Hodgdon US 869 | <<locked>> | 94% | 52,388 psi | 79% | 2910 fps | 95.5% |
| IMR 4955 Enduron | <<locked>> | 80% | 56,144 psi | 84% | 2910 fps | 100% |
| IMR 7828 SSC | <<locked>> | 80% | 53,171 psi | 80% | 2936 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 80% | 45,237 psi | 68% | 2700 fps | 95.1% |
| IMR 8133 Enduron | <<locked>> | 80% | 35,998 psi | 54% | 2612 fps | 98.4% |
| Lovex D100 | <<locked>> | 86% | 49,327 psi | 74% | 2808 fps | 95.2% |
| Lovex S071 | <<locked>> | 80% | 47,253 psi | 71% | 2726 fps | 100% |
| Norma 217 | <<locked>> | 80% | 36,956 psi | 55% | 2638 fps | 99.8% |
| Ramshot Grand | <<locked>> | 80% | 54,737 psi | 82% | 2959 fps | 100% |
| Ramshot LRT | <<locked>> | 90% | 51,155 psi | 77% | 2943 fps | 95.3% |
| Ramshot Magnum | <<locked>> | 80% | 49,472 psi | 74% | 2828 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,718 psi | 45% | 1759 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 47,674 psi | 71% | 2881 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 43,584 psi | 65% | 2789 fps | 99.1% |
| Shooters World 50 BMG | <<locked>> | 86% | 49,327 psi | 74% | 2808 fps | 95.2% |
| SNPE Vectan SP 13 | <<locked>> | 88% | 40,727 psi | 61% | 2677 fps | 95.9% |
| Vihtavuori 20N29 | <<locked>> | 94% | 44,208 psi | 66% | 2769 fps | 95.3% |
| Vihtavuori 24N41 | <<locked>> | 92% | 52,910 psi | 79% | 2923 fps | 95.6% |
| Vihtavuori N165 | <<locked>> | 80% | 51,735 psi | 78% | 2815 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 44,846 psi | 67% | 2733 fps | 96.6% |
| Vihtavuori N565 | <<locked>> | 80% | 49,284 psi | 74% | 2851 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 80% | 44,309 psi | 66% | 2799 fps | 98.9% |
| Vihtavuori N570 | 84.4 gr | 80% | 42,554 psi | 64% | 2799 fps | 96.9% |
| Winchester StaBALL HD | <<locked>> | 80% | 55,390 psi | 83% | 2940 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 54,520 psi | 82% | 2871 fps | 100% |
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 45 powders for 7.21 Firebird loaded with the .284 | 175gr | Sierra MatchKing. ADI AR 2218 delivers the highest muzzle velocity at 3,159 fps; across all powders the maximum-charge window runs from 1,919 fps to 3,159 fps. Accurate 8700 gives the best case fill at 100 %, and 45 of the 45 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (460 MPa), the top charges use 57–90 %, leaving at least 10 % headroom. The 175.0 gr projectile in 0.284" calls for a 1:10.0 twist; slower twists will usually not stabilise this weight. Accurate 8700, 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. ADI AR 2218, Vihtavuori N570, Alliant Reloder-33 rank at the top here: for 7.21 Firebird with the .284 | 175gr | Sierra MatchKing 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.