Load Specifications
Load data in caliber 7.21 Firebird with .284 | 140gr | Sierra GameKing bullet and 52 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2218, Hodgdon Retumbo and Vihtavuori N570.
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% | 58,450 psi | 88% | 3179 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 50,473 psi | 76% | 3136 fps | 96.9% |
| Accurate MAGPRO | <<locked>> | 84% | 57,682 psi | 86% | 3301 fps | 99.6% |
| ADI AR 2209 | <<locked>> | 84% | 59,321 psi | 89% | 3278 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 58,262 psi | 87% | 3297 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 57,711 psi | 87% | 3274 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 58,871 psi | 88% | 3412 fps | 99.2% |
| ADI AR 2225 | <<locked>> | 96% | 57,479 psi | 86% | 3297 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 58,900 psi | 88% | 3268 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 58,740 psi | 88% | 3291 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 56,913 psi | 85% | 3186 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 57,740 psi | 87% | 3264 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 57,827 psi | 87% | 3278 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 56,652 psi | 85% | 3310 fps | 98.6% |
| Alliant Reloder-50 | <<locked>> | 98% | 56,855 psi | 85% | 3301 fps | 98.2% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 58,421 psi | 88% | 3248 fps | 98.9% |
| Bofors RP15 | <<locked>> | 88% | 58,102 psi | 87% | 3281 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 57,696 psi | 86% | 3291 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 58,740 psi | 88% | 3291 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 59,219 psi | 89% | 3294 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 56,884 psi | 85% | 3222 fps | 99.7% |
| Hodgdon H4831 SC | <<locked>> | 86% | 59,727 psi | 90% | 3268 fps | 99.9% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 59,277 psi | 89% | 3166 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 57,493 psi | 86% | 3369 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,855 psi | 57% | 2119 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 56,869 psi | 85% | 3196 fps | 99.7% |
| IMR 7828 SSC | <<locked>> | 86% | 56,739 psi | 85% | 3281 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 92% | 59,408 psi | 89% | 3202 fps | 96.2% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 60,263 psi | 90% | 3340 fps | 100% |
| Lovex S071 | <<locked>> | 90% | 56,753 psi | 85% | 3156 fps | 100% |
| Norma 217 | <<locked>> | 98% | 57,914 psi | 87% | 3301 fps | 100% |
| Norma MRP | <<locked>> | 84% | 59,016 psi | 88% | 3304 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 58,363 psi | 87% | 3304 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 56,898 psi | 85% | 3222 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,914 psi | 58% | 2169 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 58,653 psi | 88% | 3346 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 57,725 psi | 87% | 3314 fps | 99.8% |
| Rottweil R 904 | <<locked>> | 84% | 59,364 psi | 89% | 3241 fps | 100% |
| Rottweil R 905 | <<locked>> | 84% | 58,697 psi | 88% | 3258 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 52,431 psi | 79% | 3153 fps | 96.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 58,320 psi | 87% | 3251 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 57,174 psi | 86% | 3169 fps | 99.7% |
| Somchem S385 | <<locked>> | 84% | 58,987 psi | 88% | 3219 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 59,219 psi | 89% | 3205 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 58,798 psi | 88% | 3235 fps | 97.6% |
| Vihtavuori N555 | <<locked>> | 84% | 58,610 psi | 88% | 3219 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 58,262 psi | 87% | 3310 fps | 99.8% |
| Vihtavuori N565 | <<locked>> | 90% | 59,857 psi | 90% | 3304 fps | 100% |
| Vihtavuori N568 | <<locked>> | 92% | 57,943 psi | 87% | 3317 fps | 99.5% |
| Vihtavuori N570 | <<locked>> | 94% | 59,683 psi | 89% | 3392 fps | 98.7% |
| Winchester StaBALL HD | <<locked>> | 86% | 58,117 psi | 87% | 3284 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 59,117 psi | 89% | 3222 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% | 47,688 psi | 71% | 3005 fps | 100% |
| Accurate 8700 | <<locked>> | 98% | 46,862 psi | 70% | 3064 fps | 95.8% |
| Accurate MAGPRO | <<locked>> | 80% | 49,980 psi | 75% | 3156 fps | 98.6% |
| ADI AR 2209 | <<locked>> | 80% | 51,822 psi | 78% | 3150 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 47,050 psi | 71% | 3094 fps | 98.9% |
| ADI AR 2217 | <<locked>> | 80% | 35,114 psi | 53% | 2805 fps | 95.9% |
| ADI AR 2218 | 98.8 gr | 90% | 43,511 psi | 65% | 3091 fps | 95.2% |
| ADI AR 2225 | <<locked>> | 80% | 32,532 psi | 49% | 2779 fps | 98% |
| Alliant Reloder-19 | <<locked>> | 80% | 51,517 psi | 77% | 3140 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 47,834 psi | 72% | 3097 fps | 99.6% |
| Alliant Reloder-23 | <<locked>> | 80% | 46,673 psi | 70% | 3018 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 40,799 psi | 61% | 2963 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 53,693 psi | 80% | 3212 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 88% | 45,121 psi | 68% | 3084 fps | 95.8% |
| Alliant Reloder-50 | <<locked>> | 92% | 45,281 psi | 68% | 3074 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 44,831 psi | 67% | 2989 fps | 96% |
| Bofors RP15 | <<locked>> | 80% | 44,483 psi | 67% | 3025 fps | 99.1% |
| Bofors RP30 | <<locked>> | 80% | 38,058 psi | 57% | 2890 fps | 97.1% |
| Bofors RP5 | <<locked>> | 80% | 47,834 psi | 72% | 3097 fps | 99.6% |
| Hodgdon H1000 | <<locked>> | 80% | 38,377 psi | 58% | 2897 fps | 97.8% |
| Hodgdon H4831 | <<locked>> | 80% | 49,545 psi | 74% | 3091 fps | 98.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 48,573 psi | 73% | 3071 fps | 98.7% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 55,709 psi | 84% | 3117 fps | 100% |
| Hodgdon Retumbo | 82.9 gr | 80% | 39,871 psi | 60% | 3022 fps | 99.1% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,485 psi | 43% | 1906 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 49,995 psi | 75% | 3074 fps | 99% |
| IMR 7828 SSC | <<locked>> | 80% | 45,919 psi | 69% | 3077 fps | 98.7% |
| IMR 7977 Enduron | <<locked>> | 90% | 55,564 psi | 83% | 3136 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 84% | 34,693 psi | 52% | 2818 fps | 95.6% |
| Lovex S071 | <<locked>> | 80% | 41,162 psi | 62% | 2874 fps | 99.8% |
| Norma 217 | <<locked>> | 80% | 30,414 psi | 46% | 2713 fps | 95.9% |
| Norma MRP | <<locked>> | 80% | 51,213 psi | 77% | 3173 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 46,572 psi | 70% | 3094 fps | 99.1% |
| Ramshot Magnum | <<locked>> | 80% | 42,061 psi | 63% | 2953 fps | 99.4% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,225 psi | 44% | 1949 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 39,552 psi | 59% | 2992 fps | 99.7% |
| ReloadSwiss RS 80 | <<locked>> | 82% | 39,421 psi | 59% | 2946 fps | 96% |
| Rottweil R 904 | <<locked>> | 80% | 52,257 psi | 78% | 3123 fps | 99.6% |
| Rottweil R 905 | <<locked>> | 80% | 51,314 psi | 77% | 3130 fps | 99.9% |
| SNPE Vectan SP 13 | <<locked>> | 96% | 45,600 psi | 68% | 3015 fps | 95% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 51,010 psi | 76% | 3130 fps | 99.9% |
| Somchem S361 | <<locked>> | 80% | 53,461 psi | 80% | 3107 fps | 99.4% |
| Somchem S385 | <<locked>> | 80% | 51,648 psi | 77% | 3100 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 45,295 psi | 68% | 2969 fps | 99.6% |
| Vihtavuori N170 | <<locked>> | 86% | 47,950 psi | 72% | 3038 fps | 95% |
| Vihtavuori N555 | <<locked>> | 80% | 51,358 psi | 77% | 3104 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 50,633 psi | 76% | 3173 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 80% | 42,424 psi | 64% | 2976 fps | 97.7% |
| Vihtavuori N568 | <<locked>> | 82% | 40,277 psi | 60% | 2959 fps | 95.7% |
| Vihtavuori N570 | 92.5 gr | 86% | 44,541 psi | 67% | 3094 fps | 95% |
| Winchester StaBALL HD | <<locked>> | 80% | 46,195 psi | 69% | 3094 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 47,877 psi | 72% | 3031 fps | 99.6% |
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 59 powders for 7.21 Firebird loaded with the .284 | 140gr | Sierra GameKing. ADI AR 2218 delivers the highest muzzle velocity at 3,412 fps; across all powders the maximum-charge window runs from 2,119 fps to 3,412 fps. Accurate 8700 gives the best case fill at 100 %, and 59 of the 59 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 1:10.0 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, Hodgdon Retumbo, Vihtavuori N570 rank at the top here: for 7.21 Firebird with the .284 | 140gr | Sierra GameKing they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG, Hodgdon US 869, Lovex D100 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.