Load Specifications
Load data in caliber 7.21 Firebird with .284 | 151gr | Warner Tool Co. Flat Line 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 Hodgdon Retumbo.
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>> | 86% | 59,524 psi | 89% | 3100 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 51,735 psi | 78% | 3077 fps | 97.7% |
| Accurate MAGPRO | <<locked>> | 84% | 58,827 psi | 88% | 3225 fps | 99.9% |
| ADI AR 2209 | <<locked>> | 82% | 56,492 psi | 85% | 3136 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 59,451 psi | 89% | 3219 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 58,972 psi | 88% | 3199 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 60,089 psi | 90% | 3346 fps | 99.7% |
| ADI AR 2225 | <<locked>> | 96% | 58,610 psi | 88% | 3219 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 59,799 psi | 90% | 3182 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 59,915 psi | 90% | 3209 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 58,117 psi | 87% | 3104 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 58,958 psi | 88% | 3186 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 59,205 psi | 89% | 3199 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 57,870 psi | 87% | 3245 fps | 99.1% |
| Alliant Reloder-50 | <<locked>> | 98% | 58,146 psi | 87% | 3238 fps | 98.8% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 59,350 psi | 89% | 3173 fps | 99.3% |
| Bofors RP15 | <<locked>> | 88% | 59,306 psi | 89% | 3202 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 58,842 psi | 88% | 3212 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 59,915 psi | 90% | 3209 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 56,289 psi | 84% | 3156 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 57,870 psi | 87% | 3143 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 84% | 56,695 psi | 85% | 3127 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 90% | 58,798 psi | 88% | 3291 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,029 psi | 57% | 2044 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 57,812 psi | 87% | 3117 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 86% | 57,928 psi | 87% | 3202 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 92% | 60,234 psi | 90% | 3127 fps | 97% |
| IMR 8133 Enduron | <<locked>> | 98% | 57,522 psi | 86% | 3205 fps | 100% |
| Lovex S071 | <<locked>> | 90% | 57,769 psi | 87% | 3074 fps | 100% |
| Norma 217 | <<locked>> | 98% | 59,103 psi | 89% | 3228 fps | 100% |
| Norma MRP | <<locked>> | 84% | 60,278 psi | 90% | 3225 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 59,625 psi | 89% | 3225 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 58,146 psi | 87% | 3146 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,986 psi | 58% | 2090 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 60,118 psi | 90% | 3271 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 59,030 psi | 88% | 3245 fps | 100% |
| Rottweil R 904 | <<locked>> | 84% | 60,365 psi | 90% | 3159 fps | 100% |
| Rottweil R 905 | <<locked>> | 84% | 59,843 psi | 90% | 3176 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 53,505 psi | 80% | 3087 fps | 97.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 59,451 psi | 89% | 3173 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 58,189 psi | 87% | 3091 fps | 99.9% |
| Somchem S385 | <<locked>> | 84% | 59,959 psi | 90% | 3136 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 60,191 psi | 90% | 3127 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 59,814 psi | 90% | 3166 fps | 98.3% |
| Vihtavuori N555 | <<locked>> | 84% | 59,756 psi | 90% | 3133 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 59,451 psi | 89% | 3235 fps | 100% |
| Vihtavuori N565 | <<locked>> | 88% | 56,971 psi | 85% | 3166 fps | 100% |
| Vihtavuori N568 | <<locked>> | 92% | 59,176 psi | 89% | 3245 fps | 99.8% |
| Vihtavuori N570 | <<locked>> | 92% | 56,652 psi | 85% | 3248 fps | 98.7% |
| Winchester StaBALL HD | <<locked>> | 86% | 59,509 psi | 89% | 3202 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 60,089 psi | 90% | 3140 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% | 48,646 psi | 73% | 2933 fps | 100% |
| Accurate 8700 | <<locked>> | 96% | 44,469 psi | 67% | 2936 fps | 95.8% |
| Accurate MAGPRO | <<locked>> | 80% | 51,140 psi | 77% | 3091 fps | 99.2% |
| ADI AR 2209 | <<locked>> | 80% | 52,808 psi | 79% | 3074 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 48,138 psi | 72% | 3025 fps | 99.4% |
| ADI AR 2217 | <<locked>> | 80% | 36,013 psi | 54% | 2753 fps | 97.1% |
| ADI AR 2218 | 93.7 gr | 88% | 41,321 psi | 62% | 2959 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 80% | 33,359 psi | 50% | 2726 fps | 98.9% |
| Alliant Reloder-19 | <<locked>> | 80% | 52,504 psi | 79% | 3064 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 48,892 psi | 73% | 3025 fps | 99.9% |
| Alliant Reloder-23 | <<locked>> | 80% | 47,616 psi | 71% | 2943 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 41,800 psi | 63% | 2897 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 54,882 psi | 82% | 3136 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 86% | 42,772 psi | 64% | 2953 fps | 95.7% |
| Alliant Reloder-50 | <<locked>> | 90% | 43,120 psi | 65% | 2949 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 45,716 psi | 69% | 2927 fps | 96.9% |
| Bofors RP15 | <<locked>> | 80% | 45,556 psi | 68% | 2959 fps | 99.6% |
| Bofors RP30 | <<locked>> | 80% | 38,986 psi | 58% | 2835 fps | 98% |
| Bofors RP5 | <<locked>> | 80% | 48,892 psi | 73% | 3025 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 80% | 39,189 psi | 59% | 2835 fps | 98.6% |
| Hodgdon H4831 | <<locked>> | 80% | 50,430 psi | 76% | 3018 fps | 99.3% |
| Hodgdon H4831 SC | <<locked>> | 80% | 49,545 psi | 74% | 3002 fps | 99.2% |
| Hodgdon Retumbo | 80.4 gr | 80% | 40,930 psi | 61% | 2963 fps | 99.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,500 psi | 43% | 1831 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 50,850 psi | 76% | 2999 fps | 99.5% |
| IMR 7828 SSC | <<locked>> | 80% | 46,963 psi | 70% | 3009 fps | 99.3% |
| IMR 7977 Enduron | <<locked>> | 88% | 53,026 psi | 79% | 3005 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 82% | 33,112 psi | 50% | 2697 fps | 95.6% |
| Lovex S071 | <<locked>> | 80% | 42,032 psi | 63% | 2805 fps | 100% |
| Norma 217 | <<locked>> | 80% | 31,299 psi | 47% | 2664 fps | 97.2% |
| Norma MRP | <<locked>> | 80% | 52,315 psi | 78% | 3100 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 47,703 psi | 72% | 3025 fps | 99.6% |
| Ramshot Magnum | <<locked>> | 80% | 43,120 psi | 65% | 2894 fps | 99.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,399 psi | 44% | 1877 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 40,596 psi | 61% | 2936 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 37,391 psi | 56% | 2818 fps | 96% |
| Rottweil R 904 | <<locked>> | 80% | 53,127 psi | 80% | 3041 fps | 99.8% |
| Rottweil R 905 | <<locked>> | 80% | 52,344 psi | 78% | 3054 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 94% | 43,468 psi | 65% | 2894 fps | 95% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 51,996 psi | 78% | 3054 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 54,302 psi | 81% | 3028 fps | 99.7% |
| Somchem S385 | <<locked>> | 80% | 52,663 psi | 79% | 3025 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 46,209 psi | 69% | 2897 fps | 99.9% |
| Vihtavuori N170 | <<locked>> | 84% | 45,658 psi | 68% | 2910 fps | 95% |
| Vihtavuori N555 | <<locked>> | 80% | 52,518 psi | 79% | 3025 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 51,692 psi | 77% | 3104 fps | 99.6% |
| Vihtavuori N565 | <<locked>> | 80% | 43,323 psi | 65% | 2910 fps | 98.4% |
| Vihtavuori N568 | <<locked>> | 80% | 38,348 psi | 57% | 2835 fps | 95.7% |
| Vihtavuori N570 | 87.6 gr | 84% | 42,424 psi | 64% | 2963 fps | 95% |
| Winchester StaBALL HD | <<locked>> | 80% | 47,471 psi | 71% | 3022 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 48,907 psi | 73% | 2959 fps | 99.9% |
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 58 powders for 7.21 Firebird loaded with the .284 | 151gr | Warner Tool Co. Flat Line. ADI AR 2218 delivers the highest muzzle velocity at 3,346 fps; across all powders the maximum-charge window runs from 2,044 fps to 3,346 fps. Accurate 8700 gives the best case fill at 100 %, and 58 of the 58 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 151.0 gr projectile in 0.284" calls for a 1:8.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, Hodgdon US 869 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, Hodgdon Retumbo rank at the top here: for 7.21 Firebird with the .284 | 151gr | Warner Tool Co. Flat Line they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG, Hodgdon US 869, Vihtavuori 20N29 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.