Load Specifications
Load data in caliber 7.21 Firebird with .284 | 160gr | Swift A-Frame bullet and 50 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% | 59,843 psi | 90% | 3028 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 57,159 psi | 86% | 3097 fps | 99.2% |
| Accurate MAGPRO | <<locked>> | 82% | 59,364 psi | 89% | 3156 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 59,640 psi | 89% | 3146 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 59,857 psi | 90% | 3136 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 56,768 psi | 85% | 3215 fps | 99.7% |
| ADI AR 2225 | <<locked>> | 94% | 60,017 psi | 90% | 3156 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 59,872 psi | 90% | 3107 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 60,191 psi | 90% | 3136 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 58,479 psi | 88% | 3028 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 59,828 psi | 90% | 3114 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 59,074 psi | 89% | 3189 fps | 99.6% |
| Alliant Reloder-50 | <<locked>> | 96% | 59,596 psi | 89% | 3189 fps | 99.4% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 59,466 psi | 89% | 3104 fps | 99.7% |
| Bofors RP15 | <<locked>> | 86% | 59,741 psi | 90% | 3130 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 59,828 psi | 90% | 3150 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 60,191 psi | 90% | 3136 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 57,072 psi | 86% | 3091 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 57,870 psi | 87% | 3071 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 56,942 psi | 85% | 3058 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 60,147 psi | 90% | 3222 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,116 psi | 57% | 2001 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,667 psi | 86% | 3045 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 58,494 psi | 88% | 3133 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 60,292 psi | 90% | 3064 fps | 97.7% |
| IMR 8133 Enduron | <<locked>> | 96% | 58,813 psi | 88% | 3146 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 58,421 psi | 88% | 3061 fps | 96.5% |
| Lovex S071 | <<locked>> | 88% | 58,320 psi | 87% | 3009 fps | 100% |
| Norma 217 | <<locked>> | 94% | 56,666 psi | 85% | 3110 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 60,336 psi | 90% | 3159 fps | 100% |
| Ramshot Magnum | <<locked>> | 86% | 58,813 psi | 88% | 3077 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,247 psi | 59% | 2047 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 56,840 psi | 85% | 3140 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 60,292 psi | 90% | 3186 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 60,249 psi | 90% | 3084 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 60,002 psi | 90% | 3100 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 58,421 psi | 88% | 3061 fps | 96.5% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 58,436 psi | 88% | 3100 fps | 99% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,640 psi | 89% | 3100 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 60,191 psi | 90% | 3064 fps | 100% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 51,909 psi | 78% | 3009 fps | 96.6% |
| Vihtavuori N165 | <<locked>> | 84% | 56,666 psi | 85% | 3002 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 60,191 psi | 90% | 3104 fps | 98.9% |
| Vihtavuori N555 | <<locked>> | 82% | 60,147 psi | 90% | 3061 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 59,756 psi | 90% | 3159 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 57,696 psi | 86% | 3104 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 60,162 psi | 90% | 3182 fps | 100% |
| Vihtavuori N570 | <<locked>> | 90% | 57,841 psi | 87% | 3192 fps | 99.3% |
| Winchester StaBALL HD | <<locked>> | 82% | 56,550 psi | 85% | 3074 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 60,162 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% | 52,446 psi | 79% | 2920 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 42,453 psi | 64% | 2828 fps | 95.9% |
| Accurate MAGPRO | <<locked>> | 80% | 55,317 psi | 83% | 3091 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 52,011 psi | 78% | 3022 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 39,189 psi | 59% | 2766 fps | 98.7% |
| ADI AR 2218 | 92.2 gr | 84% | 38,957 psi | 58% | 2835 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 80% | 36,521 psi | 55% | 2740 fps | 99.8% |
| Alliant Reloder-19 | <<locked>> | 80% | 56,231 psi | 84% | 3051 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 52,721 psi | 79% | 3018 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 51,401 psi | 77% | 2923 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 45,542 psi | 68% | 2890 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 40,611 psi | 61% | 2831 fps | 95.7% |
| Alliant Reloder-50 | 95.9 gr | 86% | 41,191 psi | 62% | 2835 fps | 95.3% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 48,921 psi | 73% | 2923 fps | 98.3% |
| Bofors RP15 | <<locked>> | 80% | 49,095 psi | 74% | 2956 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 42,641 psi | 64% | 2844 fps | 99.3% |
| Bofors RP5 | <<locked>> | 80% | 52,721 psi | 79% | 3018 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 42,786 psi | 64% | 2841 fps | 99.6% |
| Hodgdon H4831 | <<locked>> | 80% | 54,070 psi | 81% | 3012 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 53,185 psi | 80% | 2995 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 80% | 44,976 psi | 67% | 2969 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,732 psi | 43% | 1795 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 54,041 psi | 81% | 2986 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 50,778 psi | 76% | 3005 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 84% | 49,690 psi | 74% | 2884 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 80% | 34,084 psi | 51% | 2654 fps | 96.8% |
| Lovex D100 | <<locked>> | 90% | 54,288 psi | 81% | 2992 fps | 95.6% |
| Lovex S071 | <<locked>> | 80% | 45,252 psi | 68% | 2799 fps | 100% |
| Norma 217 | <<locked>> | 80% | 34,722 psi | 52% | 2684 fps | 98.9% |
| Ramshot Grand | <<locked>> | 80% | 51,996 psi | 78% | 3028 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 47,137 psi | 71% | 2894 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,515 psi | 44% | 1837 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 45,107 psi | 68% | 2946 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 41,350 psi | 62% | 2838 fps | 98% |
| Rottweil R 904 | <<locked>> | 80% | 56,550 psi | 85% | 3028 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 56,260 psi | 84% | 3045 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 54,288 psi | 81% | 2992 fps | 95.6% |
| SNPE Vectan SP 13 | <<locked>> | 90% | 41,466 psi | 62% | 2785 fps | 95.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 55,912 psi | 84% | 3041 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 56,376 psi | 85% | 3009 fps | 100% |
| Vihtavuori 20N29 | <<locked>> | 98% | 48,240 psi | 72% | 2940 fps | 95.6% |
| Vihtavuori N165 | <<locked>> | 80% | 49,690 psi | 74% | 2890 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 42,975 psi | 64% | 2789 fps | 95% |
| Vihtavuori N555 | <<locked>> | 80% | 56,449 psi | 85% | 3009 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 55,869 psi | 84% | 3100 fps | 100% |
| Vihtavuori N565 | <<locked>> | 80% | 46,992 psi | 70% | 2917 fps | 99.5% |
| Vihtavuori N568 | <<locked>> | 80% | 42,105 psi | 63% | 2851 fps | 97.7% |
| Vihtavuori N570 | 86.1 gr | 80% | 40,306 psi | 60% | 2844 fps | 95.1% |
| Winchester StaBALL HD | <<locked>> | 80% | 52,533 psi | 79% | 3015 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 52,489 psi | 79% | 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 54 powders for 7.21 Firebird loaded with the .284 | 160gr | Swift A-Frame. Hodgdon Retumbo delivers the highest muzzle velocity at 3,222 fps; across all powders the maximum-charge window runs from 2,001 fps to 3,222 fps. Accurate 8700 gives the best case fill at 100 %, and 54 of the 54 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 1:11.5 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 | Swift A-Frame they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG 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.