Load Specifications
Load data in caliber 7.21 Firebird with .284 | 160gr | Sierra GameKing bullet and 51 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-50.
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>> | 84% | 59,901 psi | 90% | 3031 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 56,971 psi | 85% | 3097 fps | 99.1% |
| Accurate MAGPRO | <<locked>> | 82% | 59,234 psi | 89% | 3156 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 60,336 psi | 90% | 3120 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 59,683 psi | 89% | 3150 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 59,872 psi | 90% | 3136 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 56,797 psi | 85% | 3219 fps | 99.7% |
| ADI AR 2225 | <<locked>> | 94% | 60,089 psi | 90% | 3156 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 59,915 psi | 90% | 3107 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 60,205 psi | 90% | 3136 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 58,537 psi | 88% | 3031 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 59,843 psi | 90% | 3117 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 59,132 psi | 89% | 3189 fps | 99.6% |
| Alliant Reloder-50 | <<locked>> | 96% | 59,625 psi | 89% | 3186 fps | 99.4% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 59,335 psi | 89% | 3104 fps | 99.7% |
| Bofors RP15 | <<locked>> | 86% | 59,756 psi | 90% | 3130 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 59,857 psi | 90% | 3150 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 60,205 psi | 90% | 3136 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 57,087 psi | 86% | 3091 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 57,885 psi | 87% | 3074 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 56,782 psi | 85% | 3054 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 60,162 psi | 90% | 3225 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,145 psi | 57% | 2001 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,537 psi | 86% | 3045 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 58,305 psi | 87% | 3130 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 60,147 psi | 90% | 3064 fps | 97.7% |
| IMR 8133 Enduron | <<locked>> | 96% | 58,827 psi | 88% | 3146 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 58,305 psi | 87% | 3061 fps | 96.5% |
| Lovex S071 | <<locked>> | 88% | 58,363 psi | 87% | 3009 fps | 100% |
| Norma 217 | <<locked>> | 94% | 56,681 psi | 85% | 3110 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 60,350 psi | 90% | 3159 fps | 100% |
| Ramshot Magnum | <<locked>> | 86% | 58,639 psi | 88% | 3077 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,262 psi | 59% | 2047 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 56,855 psi | 85% | 3143 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 60,118 psi | 90% | 3186 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 60,307 psi | 90% | 3087 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 60,031 psi | 90% | 3104 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 58,305 psi | 87% | 3061 fps | 96.5% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 58,465 psi | 88% | 3104 fps | 99.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,654 psi | 89% | 3100 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 60,060 psi | 90% | 3064 fps | 100% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 51,793 psi | 78% | 3009 fps | 96.6% |
| Vihtavuori N165 | <<locked>> | 84% | 56,681 psi | 85% | 3002 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 60,234 psi | 90% | 3107 fps | 98.9% |
| Vihtavuori N555 | <<locked>> | 82% | 60,191 psi | 90% | 3061 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 59,799 psi | 90% | 3163 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 57,537 psi | 86% | 3100 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 60,191 psi | 90% | 3186 fps | 100% |
| Vihtavuori N570 | <<locked>> | 90% | 57,856 psi | 87% | 3196 fps | 99.3% |
| Winchester StaBALL HD | <<locked>> | 82% | 56,594 psi | 85% | 3074 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 60,031 psi | 90% | 3064 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% | 52,301 psi | 78% | 2920 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 42,351 psi | 63% | 2828 fps | 95.9% |
| Accurate MAGPRO | <<locked>> | 80% | 55,187 psi | 83% | 3091 fps | 99.9% |
| ADI AR 2209 | <<locked>> | 80% | 56,536 psi | 85% | 3061 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 51,880 psi | 78% | 3022 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 39,204 psi | 59% | 2766 fps | 98.7% |
| ADI AR 2218 | 92.2 gr | 84% | 39,001 psi | 58% | 2838 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 80% | 36,521 psi | 55% | 2736 fps | 99.8% |
| Alliant Reloder-19 | <<locked>> | 80% | 56,086 psi | 84% | 3051 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 52,605 psi | 79% | 3018 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 51,416 psi | 77% | 2927 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 45,571 psi | 68% | 2894 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 40,640 psi | 61% | 2835 fps | 95.7% |
| Alliant Reloder-50 | 95.9 gr | 86% | 41,234 psi | 62% | 2835 fps | 95.3% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 48,791 psi | 73% | 2923 fps | 98.3% |
| Bofors RP15 | <<locked>> | 80% | 49,124 psi | 74% | 2956 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 42,511 psi | 64% | 2844 fps | 99.3% |
| Bofors RP5 | <<locked>> | 80% | 52,605 psi | 79% | 3018 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 42,801 psi | 64% | 2841 fps | 99.6% |
| Hodgdon H4831 | <<locked>> | 80% | 54,085 psi | 81% | 3012 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 53,040 psi | 80% | 2995 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 80% | 45,005 psi | 67% | 2972 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,732 psi | 43% | 1795 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 54,056 psi | 81% | 2986 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 50,836 psi | 76% | 3009 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 84% | 49,559 psi | 74% | 2884 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 80% | 34,113 psi | 51% | 2654 fps | 96.8% |
| Lovex D100 | <<locked>> | 90% | 54,331 psi | 81% | 2995 fps | 95.6% |
| Lovex S071 | <<locked>> | 80% | 45,266 psi | 68% | 2799 fps | 100% |
| Norma 217 | <<locked>> | 80% | 34,751 psi | 52% | 2684 fps | 98.9% |
| Ramshot Grand | <<locked>> | 80% | 52,025 psi | 78% | 3028 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 47,007 psi | 70% | 2894 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,530 psi | 44% | 1837 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 44,976 psi | 67% | 2943 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 41,234 psi | 62% | 2838 fps | 97.9% |
| Rottweil R 904 | <<locked>> | 80% | 56,608 psi | 85% | 3031 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 56,115 psi | 84% | 3045 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 54,331 psi | 81% | 2995 fps | 95.6% |
| SNPE Vectan SP 13 | <<locked>> | 90% | 41,481 psi | 62% | 2789 fps | 95.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 55,767 psi | 84% | 3041 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 56,246 psi | 84% | 3009 fps | 100% |
| Vihtavuori 20N29 | <<locked>> | 98% | 48,269 psi | 72% | 2940 fps | 95.6% |
| Vihtavuori N165 | <<locked>> | 80% | 49,574 psi | 74% | 2887 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 42,873 psi | 64% | 2789 fps | 95% |
| Vihtavuori N555 | <<locked>> | 80% | 56,304 psi | 84% | 3005 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 55,738 psi | 84% | 3097 fps | 100% |
| Vihtavuori N565 | <<locked>> | 80% | 47,021 psi | 70% | 2917 fps | 99.5% |
| Vihtavuori N568 | <<locked>> | 80% | 42,119 psi | 63% | 2854 fps | 97.7% |
| Vihtavuori N570 | 86 gr | 80% | 40,190 psi | 60% | 2841 fps | 95% |
| Winchester StaBALL HD | <<locked>> | 80% | 52,402 psi | 79% | 3015 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 52,359 psi | 78% | 2949 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 51 powders for 7.21 Firebird loaded with the .284 | 160gr | Sierra GameKing. Hodgdon Retumbo delivers the highest muzzle velocity at 3,225 fps; across all powders the maximum-charge window runs from 2,001 fps to 3,225 fps. Accurate 8700 gives the best case fill at 100 %, and 51 of the 51 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 160.0 gr projectile in 0.284" calls for a 1:11.0 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-50 rank at the top here: for 7.21 Firebird with the .284 | 160gr | Sierra GameKing 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.