Load Specifications
Load data in caliber 7.21 Firebird with .284 | 140gr | Alaska Bullet Works Kodiak SP SPBC 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 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% | 59,654 psi | 89% | 3196 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 52,127 psi | 78% | 3163 fps | 97.3% |
| Accurate MAGPRO | <<locked>> | 84% | 59,088 psi | 89% | 3320 fps | 99.7% |
| ADI AR 2209 | <<locked>> | 84% | 60,365 psi | 90% | 3291 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 59,509 psi | 89% | 3314 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 59,103 psi | 89% | 3291 fps | 100% |
| ADI AR 2218 | <<locked>> | 96% | 56,028 psi | 84% | 3356 fps | 98.8% |
| ADI AR 2225 | <<locked>> | 96% | 59,088 psi | 89% | 3314 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 59,915 psi | 90% | 3281 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 59,973 psi | 90% | 3304 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 58,030 psi | 87% | 3199 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 59,190 psi | 89% | 3281 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 59,379 psi | 89% | 3294 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 58,276 psi | 87% | 3333 fps | 98.9% |
| Alliant Reloder-50 | <<locked>> | 98% | 58,639 psi | 88% | 3323 fps | 98.5% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 59,495 psi | 89% | 3264 fps | 99.1% |
| Bofors RP15 | <<locked>> | 88% | 59,321 psi | 89% | 3294 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 59,074 psi | 89% | 3307 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 59,973 psi | 90% | 3304 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 56,405 psi | 85% | 3248 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 57,827 psi | 87% | 3235 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 84% | 56,913 psi | 85% | 3222 fps | 99.7% |
| Hodgdon Retumbo | <<locked>> | 90% | 58,943 psi | 88% | 3383 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,971 psi | 57% | 2129 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 57,783 psi | 87% | 3209 fps | 99.8% |
| IMR 7828 SSC | <<locked>> | 86% | 58,030 psi | 87% | 3297 fps | 100% |
| IMR 8133 Enduron | <<locked>> | 98% | 57,841 psi | 87% | 3297 fps | 100% |
| Lovex S071 | <<locked>> | 90% | 57,957 psi | 87% | 3173 fps | 100% |
| Norma 217 | <<locked>> | 98% | 59,350 psi | 89% | 3320 fps | 100% |
| Norma MRP | <<locked>> | 84% | 60,278 psi | 90% | 3317 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 59,901 psi | 90% | 3323 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 58,291 psi | 87% | 3238 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,015 psi | 58% | 2178 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 60,365 psi | 90% | 3366 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 59,437 psi | 89% | 3337 fps | 99.9% |
| Rottweil R 904 | <<locked>> | 82% | 56,724 psi | 85% | 3199 fps | 99.9% |
| Rottweil R 905 | <<locked>> | 84% | 59,814 psi | 90% | 3271 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 53,824 psi | 81% | 3173 fps | 97.3% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 59,437 psi | 89% | 3268 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 58,189 psi | 87% | 3182 fps | 99.8% |
| Somchem S385 | <<locked>> | 84% | 60,162 psi | 90% | 3235 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 60,350 psi | 90% | 3219 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 60,075 psi | 90% | 3258 fps | 97.9% |
| Vihtavuori N555 | <<locked>> | 84% | 59,814 psi | 90% | 3232 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 59,466 psi | 89% | 3327 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 88% | 57,116 psi | 86% | 3258 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 92% | 59,408 psi | 89% | 3337 fps | 99.7% |
| Vihtavuori N570 | <<locked>> | 92% | 56,942 psi | 85% | 3340 fps | 98.3% |
| Winchester StaBALL HD | <<locked>> | 86% | 59,857 psi | 90% | 3301 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 60,249 psi | 90% | 3235 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% | 48,718 psi | 73% | 3018 fps | 100% |
| Accurate 8700 | <<locked>> | 96% | 44,744 psi | 67% | 3018 fps | 95.2% |
| Accurate MAGPRO | <<locked>> | 80% | 51,169 psi | 77% | 3176 fps | 98.8% |
| ADI AR 2209 | <<locked>> | 80% | 52,881 psi | 79% | 3169 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 48,109 psi | 72% | 3114 fps | 99.1% |
| ADI AR 2217 | <<locked>> | 80% | 35,969 psi | 54% | 2828 fps | 96.4% |
| ADI AR 2218 | 100.7 gr | 90% | 44,672 psi | 67% | 3117 fps | 95.8% |
| ADI AR 2225 | <<locked>> | 80% | 33,373 psi | 50% | 2795 fps | 98.3% |
| Alliant Reloder-19 | <<locked>> | 80% | 52,576 psi | 79% | 3156 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 48,892 psi | 73% | 3114 fps | 99.8% |
| Alliant Reloder-23 | <<locked>> | 80% | 47,645 psi | 71% | 3035 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 41,858 psi | 63% | 2982 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 55,027 psi | 82% | 3228 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 86% | 43,047 psi | 65% | 3031 fps | 95.1% |
| Alliant Reloder-50 | <<locked>> | 92% | 46,760 psi | 70% | 3097 fps | 95.8% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 45,774 psi | 69% | 3009 fps | 96.4% |
| Bofors RP15 | <<locked>> | 80% | 45,527 psi | 68% | 3045 fps | 99.3% |
| Bofors RP30 | <<locked>> | 80% | 39,059 psi | 59% | 2910 fps | 97.4% |
| Bofors RP5 | <<locked>> | 80% | 48,892 psi | 73% | 3114 fps | 99.8% |
| Hodgdon H1000 | <<locked>> | 80% | 39,175 psi | 59% | 2910 fps | 98.1% |
| Hodgdon H4831 | <<locked>> | 80% | 50,531 psi | 76% | 3107 fps | 99.1% |
| Hodgdon H4831 SC | <<locked>> | 80% | 49,559 psi | 74% | 3087 fps | 98.9% |
| Hodgdon Retumbo | 84.5 gr | 80% | 40,930 psi | 61% | 3041 fps | 99.3% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,500 psi | 43% | 1909 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 50,937 psi | 76% | 3091 fps | 99.2% |
| IMR 7828 SSC | <<locked>> | 80% | 46,992 psi | 70% | 3097 fps | 99% |
| IMR 8133 Enduron | <<locked>> | 84% | 35,621 psi | 53% | 2838 fps | 96% |
| Lovex S071 | <<locked>> | 80% | 41,930 psi | 63% | 2890 fps | 99.9% |
| Norma 217 | <<locked>> | 80% | 31,285 psi | 47% | 2730 fps | 96.4% |
| Norma MRP | <<locked>> | 80% | 52,460 psi | 79% | 3192 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 47,688 psi | 71% | 3114 fps | 99.3% |
| Ramshot Magnum | <<locked>> | 80% | 43,178 psi | 65% | 2972 fps | 99.6% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,356 psi | 44% | 1955 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 40,683 psi | 61% | 3015 fps | 99.8% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 37,449 psi | 56% | 2887 fps | 95.2% |
| Rottweil R 904 | <<locked>> | 80% | 53,098 psi | 80% | 3136 fps | 99.7% |
| Rottweil R 905 | <<locked>> | 80% | 52,417 psi | 79% | 3150 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 96% | 46,789 psi | 70% | 3038 fps | 95.4% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 52,098 psi | 78% | 3146 fps | 99.9% |
| Somchem S361 | <<locked>> | 80% | 54,462 psi | 82% | 3123 fps | 99.5% |
| Somchem S385 | <<locked>> | 80% | 52,678 psi | 79% | 3117 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 46,267 psi | 69% | 2986 fps | 99.7% |
| Vihtavuori N170 | <<locked>> | 86% | 48,921 psi | 73% | 3054 fps | 95.4% |
| Vihtavuori N555 | <<locked>> | 80% | 52,518 psi | 79% | 3120 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 51,822 psi | 78% | 3192 fps | 99.3% |
| Vihtavuori N565 | <<locked>> | 80% | 43,395 psi | 65% | 2992 fps | 98% |
| Vihtavuori N568 | <<locked>> | 80% | 38,435 psi | 58% | 2910 fps | 95% |
| Vihtavuori N570 | 94.2 gr | 86% | 45,672 psi | 68% | 3114 fps | 95.5% |
| Winchester StaBALL HD | <<locked>> | 80% | 47,688 psi | 71% | 3110 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 48,834 psi | 73% | 3045 fps | 99.7% |
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 | 140gr | Alaska Bullet Works Kodiak SP SPBC. Hodgdon Retumbo delivers the highest muzzle velocity at 3,383 fps; across all powders the maximum-charge window runs from 2,129 fps to 3,383 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 140.0 gr projectile in 0.284" calls for a 1:12.5 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 | 140gr | Alaska Bullet Works Kodiak SP SPBC 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.