Load Specifications
Load data in caliber 7.21 Firebird with .284 | 140gr | Sierra SBT 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 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% | 59,785 psi | 90% | 3199 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 52,156 psi | 78% | 3166 fps | 97.4% |
| Accurate MAGPRO | <<locked>> | 86% | 60,220 psi | 90% | 3333 fps | 99.6% |
| ADI AR 2209 | <<locked>> | 82% | 56,739 psi | 85% | 3235 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 59,611 psi | 89% | 3317 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 59,437 psi | 89% | 3297 fps | 100% |
| ADI AR 2218 | <<locked>> | 96% | 56,333 psi | 84% | 3363 fps | 98.9% |
| ADI AR 2225 | <<locked>> | 96% | 59,219 psi | 89% | 3317 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 60,017 psi | 90% | 3281 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 60,118 psi | 90% | 3307 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 58,349 psi | 87% | 3202 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 59,292 psi | 89% | 3284 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 59,480 psi | 89% | 3297 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 58,392 psi | 88% | 3337 fps | 98.9% |
| Alliant Reloder-50 | <<locked>> | 98% | 58,885 psi | 88% | 3333 fps | 98.6% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 59,741 psi | 90% | 3271 fps | 99.1% |
| Bofors RP15 | <<locked>> | 88% | 59,466 psi | 89% | 3297 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 59,205 psi | 89% | 3310 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 60,118 psi | 90% | 3307 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 56,942 psi | 85% | 3258 fps | 100% |
| Hodgdon H4831 | <<locked>> | 88% | 58,102 psi | 87% | 3241 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 84% | 57,014 psi | 85% | 3222 fps | 99.7% |
| Hodgdon Retumbo | <<locked>> | 90% | 59,306 psi | 89% | 3392 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,000 psi | 57% | 2129 fps | 100% |
| IMR 4831 | <<locked>> | 82% | 57,711 psi | 87% | 3176 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 57,885 psi | 87% | 3215 fps | 99.8% |
| IMR 7828 SSC | <<locked>> | 84% | 57,957 psi | 87% | 3297 fps | 100% |
| IMR 8133 Enduron | <<locked>> | 98% | 57,957 psi | 87% | 3301 fps | 100% |
| Lovex S071 | <<locked>> | 90% | 58,102 psi | 87% | 3173 fps | 100% |
| Norma 217 | <<locked>> | 98% | 59,683 psi | 89% | 3327 fps | 100% |
| Norma MRP | <<locked>> | 82% | 56,492 psi | 85% | 3261 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 58,421 psi | 88% | 3301 fps | 100% |
| Ramshot Magnum | <<locked>> | 86% | 60,162 psi | 90% | 3264 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,044 psi | 59% | 2178 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 56,086 psi | 84% | 3301 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 59,712 psi | 90% | 3340 fps | 99.9% |
| Rottweil R 904 | <<locked>> | 82% | 56,840 psi | 85% | 3202 fps | 99.9% |
| Rottweil R 905 | <<locked>> | 84% | 60,118 psi | 90% | 3278 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 54,114 psi | 81% | 3179 fps | 97.4% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 59,741 psi | 90% | 3274 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 58,479 psi | 88% | 3189 fps | 99.8% |
| Somchem S385 | <<locked>> | 84% | 60,307 psi | 90% | 3238 fps | 100% |
| Vihtavuori N165 | <<locked>> | 86% | 56,608 psi | 85% | 3166 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 60,350 psi | 90% | 3261 fps | 98% |
| Vihtavuori N555 | <<locked>> | 84% | 59,930 psi | 90% | 3235 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 59,756 psi | 90% | 3333 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 88% | 57,421 psi | 86% | 3264 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 92% | 59,727 psi | 90% | 3343 fps | 99.7% |
| Vihtavuori N570 | <<locked>> | 92% | 57,232 psi | 86% | 3346 fps | 98.4% |
| Winchester StaBALL HD | <<locked>> | 86% | 60,031 psi | 90% | 3304 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 57,334 psi | 86% | 3192 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% | 48,834 psi | 73% | 3022 fps | 100% |
| Accurate 8700 | <<locked>> | 96% | 44,991 psi | 67% | 3022 fps | 95.3% |
| Accurate MAGPRO | <<locked>> | 80% | 48,660 psi | 73% | 3120 fps | 97.9% |
| ADI AR 2209 | <<locked>> | 80% | 52,997 psi | 79% | 3173 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 48,240 psi | 72% | 3117 fps | 99.1% |
| ADI AR 2217 | <<locked>> | 80% | 36,071 psi | 54% | 2831 fps | 96.4% |
| ADI AR 2218 | 100.9 gr | 90% | 44,759 psi | 67% | 3120 fps | 95.9% |
| ADI AR 2225 | <<locked>> | 80% | 33,475 psi | 50% | 2799 fps | 98.4% |
| Alliant Reloder-19 | <<locked>> | 80% | 52,692 psi | 79% | 3159 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 49,008 psi | 73% | 3117 fps | 99.8% |
| Alliant Reloder-23 | <<locked>> | 80% | 47,776 psi | 72% | 3038 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 41,989 psi | 63% | 2986 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 55,172 psi | 83% | 3232 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 86% | 43,134 psi | 65% | 3035 fps | 95.2% |
| Alliant Reloder-50 | <<locked>> | 92% | 46,847 psi | 70% | 3100 fps | 95.8% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 45,847 psi | 69% | 3012 fps | 96.5% |
| Bofors RP15 | <<locked>> | 80% | 45,643 psi | 68% | 3048 fps | 99.4% |
| Bofors RP30 | <<locked>> | 80% | 39,160 psi | 59% | 2913 fps | 97.5% |
| Bofors RP5 | <<locked>> | 80% | 49,008 psi | 73% | 3117 fps | 99.8% |
| Hodgdon H1000 | <<locked>> | 80% | 37,057 psi | 56% | 2858 fps | 97.4% |
| Hodgdon H4831 | <<locked>> | 80% | 44,614 psi | 67% | 2989 fps | 98% |
| Hodgdon H4831 SC | <<locked>> | 80% | 49,676 psi | 74% | 3091 fps | 98.9% |
| Hodgdon Retumbo | 84.7 gr | 80% | 41,089 psi | 62% | 3045 fps | 99.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,543 psi | 43% | 1913 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 54,041 psi | 81% | 3120 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 51,039 psi | 77% | 3094 fps | 99.2% |
| IMR 7828 SSC | <<locked>> | 80% | 50,212 psi | 75% | 3159 fps | 99.4% |
| IMR 8133 Enduron | <<locked>> | 84% | 35,723 psi | 54% | 2841 fps | 96.1% |
| Lovex S071 | <<locked>> | 80% | 42,018 psi | 63% | 2894 fps | 99.9% |
| Norma 217 | <<locked>> | 80% | 31,401 psi | 47% | 2736 fps | 96.5% |
| Norma MRP | <<locked>> | 80% | 52,576 psi | 79% | 3196 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 53,998 psi | 81% | 3228 fps | 99.9% |
| Ramshot Magnum | <<locked>> | 80% | 47,674 psi | 71% | 3064 fps | 99.9% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,269 psi | 44% | 1955 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 40,814 psi | 61% | 3015 fps | 99.8% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 37,695 psi | 56% | 2897 fps | 95.4% |
| Rottweil R 904 | <<locked>> | 80% | 53,214 psi | 80% | 3140 fps | 99.7% |
| Rottweil R 905 | <<locked>> | 80% | 52,562 psi | 79% | 3156 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 96% | 47,036 psi | 71% | 3045 fps | 95.6% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 52,214 psi | 78% | 3150 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 54,549 psi | 82% | 3123 fps | 99.6% |
| Somchem S385 | <<locked>> | 80% | 52,794 psi | 79% | 3120 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 46,369 psi | 70% | 2989 fps | 99.7% |
| Vihtavuori N170 | <<locked>> | 86% | 49,153 psi | 74% | 3061 fps | 95.5% |
| Vihtavuori N555 | <<locked>> | 80% | 52,649 psi | 79% | 3123 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 51,938 psi | 78% | 3196 fps | 99.3% |
| Vihtavuori N565 | <<locked>> | 80% | 43,497 psi | 65% | 2995 fps | 98% |
| Vihtavuori N568 | <<locked>> | 80% | 38,551 psi | 58% | 2913 fps | 95.1% |
| Vihtavuori N570 | 94.5 gr | 86% | 45,963 psi | 69% | 3123 fps | 95.6% |
| Winchester StaBALL HD | <<locked>> | 80% | 47,834 psi | 72% | 3114 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 53,417 psi | 80% | 3127 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 | 140gr | Sierra SBT GameKing. Hodgdon Retumbo delivers the highest muzzle velocity at 3,392 fps; across all powders the maximum-charge window runs from 2,129 fps to 3,392 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 140.0 gr projectile in 0.284" calls for a 1:12.0 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, Hodgdon Retumbo rank at the top here: for 7.21 Firebird with the .284 | 140gr | Sierra SBT 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.