Load Specifications
Load data in caliber 7.21 Firebird with .284 | 140gr | Barnes X BT bullet and 50 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Hodgdon Retumbo, ADI AR 2218 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>> | 84% | 59,045 psi | 89% | 3176 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 54,766 psi | 82% | 3205 fps | 97.8% |
| Accurate MAGPRO | <<locked>> | 84% | 58,552 psi | 88% | 3297 fps | 99.4% |
| ADI AR 2209 | <<locked>> | 82% | 58,465 psi | 88% | 3255 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 57,551 psi | 86% | 3278 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 92% | 57,392 psi | 86% | 3261 fps | 100% |
| ADI AR 2218 | <<locked>> | 96% | 58,407 psi | 88% | 3399 fps | 99.2% |
| ADI AR 2225 | <<locked>> | 94% | 57,464 psi | 86% | 3287 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 58,204 psi | 87% | 3245 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 58,465 psi | 88% | 3274 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 56,971 psi | 85% | 3176 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 57,740 psi | 87% | 3258 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 56,913 psi | 85% | 3307 fps | 98.6% |
| Alliant Reloder-50 | <<locked>> | 96% | 57,928 psi | 87% | 3310 fps | 98.4% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 57,290 psi | 86% | 3222 fps | 98.8% |
| Bofors RP15 | <<locked>> | 86% | 58,044 psi | 87% | 3264 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 58,073 psi | 87% | 3284 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 58,465 psi | 88% | 3274 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 59,016 psi | 88% | 3281 fps | 100% |
| Hodgdon H4831 | <<locked>> | 88% | 60,031 psi | 90% | 3264 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 84% | 58,885 psi | 88% | 3245 fps | 99.8% |
| Hodgdon Retumbo | <<locked>> | 88% | 57,377 psi | 86% | 3356 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,261 psi | 57% | 2126 fps | 100% |
| IMR 4831 | <<locked>> | 82% | 59,973 psi | 90% | 3199 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 59,698 psi | 89% | 3232 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 84% | 60,031 psi | 90% | 3323 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 58,363 psi | 87% | 3176 fps | 96% |
| IMR 8133 Enduron | <<locked>> | 96% | 56,927 psi | 85% | 3281 fps | 100% |
| Lovex S071 | <<locked>> | 88% | 57,609 psi | 86% | 3156 fps | 100% |
| Norma 217 | <<locked>> | 96% | 58,494 psi | 88% | 3304 fps | 100% |
| Norma MRP | <<locked>> | 82% | 58,900 psi | 88% | 3291 fps | 100% |
| Ramshot Magnum | <<locked>> | 84% | 58,204 psi | 87% | 3232 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,262 psi | 59% | 2172 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 58,552 psi | 88% | 3337 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 58,044 psi | 87% | 3310 fps | 99.8% |
| Rottweil R 904 | <<locked>> | 82% | 58,639 psi | 88% | 3222 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 58,465 psi | 88% | 3241 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 56,666 psi | 85% | 3219 fps | 97.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 58,088 psi | 87% | 3238 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 60,278 psi | 90% | 3209 fps | 99.9% |
| Somchem S385 | <<locked>> | 82% | 58,784 psi | 88% | 3205 fps | 100% |
| Vihtavuori N165 | <<locked>> | 86% | 58,755 psi | 88% | 3189 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 58,755 psi | 88% | 3225 fps | 97.6% |
| Vihtavuori N555 | <<locked>> | 82% | 58,885 psi | 88% | 3209 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 57,899 psi | 87% | 3294 fps | 99.8% |
| Vihtavuori N565 | <<locked>> | 88% | 60,133 psi | 90% | 3301 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 58,117 psi | 87% | 3314 fps | 99.6% |
| Vihtavuori N570 | <<locked>> | 92% | 59,611 psi | 89% | 3383 fps | 98.7% |
| Winchester StaBALL HD | <<locked>> | 84% | 58,552 psi | 88% | 3278 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 59,495 psi | 89% | 3215 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% | 51,880 psi | 78% | 3064 fps | 100% |
| Accurate 8700 | <<locked>> | 94% | 44,280 psi | 66% | 3002 fps | 95% |
| Accurate MAGPRO | <<locked>> | 80% | 51,126 psi | 77% | 3163 fps | 98.4% |
| ADI AR 2209 | <<locked>> | 80% | 54,868 psi | 82% | 3196 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 50,314 psi | 75% | 3146 fps | 99.4% |
| ADI AR 2217 | <<locked>> | 80% | 38,348 psi | 57% | 2884 fps | 97.3% |
| ADI AR 2218 | 96.7 gr | 88% | 43,976 psi | 66% | 3094 fps | 95.5% |
| ADI AR 2225 | <<locked>> | 80% | 36,056 psi | 54% | 2867 fps | 99.2% |
| Alliant Reloder-19 | <<locked>> | 80% | 54,607 psi | 82% | 3186 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 51,343 psi | 77% | 3153 fps | 99.9% |
| Alliant Reloder-23 | <<locked>> | 80% | 50,140 psi | 75% | 3071 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 44,396 psi | 67% | 3025 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 84% | 42,728 psi | 64% | 3022 fps | 95% |
| Alliant Reloder-50 | <<locked>> | 90% | 46,934 psi | 70% | 3100 fps | 95.9% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 47,442 psi | 71% | 3035 fps | 96.8% |
| Bofors RP15 | <<locked>> | 80% | 47,950 psi | 72% | 3087 fps | 99.6% |
| Bofors RP30 | <<locked>> | 80% | 41,930 psi | 63% | 2972 fps | 98.3% |
| Bofors RP5 | <<locked>> | 80% | 51,343 psi | 77% | 3153 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 80% | 39,363 psi | 59% | 2907 fps | 98.2% |
| Hodgdon H4831 | <<locked>> | 80% | 46,746 psi | 70% | 3022 fps | 98.4% |
| Hodgdon H4831 SC | <<locked>> | 80% | 51,663 psi | 77% | 3120 fps | 99.2% |
| Hodgdon Retumbo | 83 gr | 80% | 43,497 psi | 65% | 3097 fps | 99.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,790 psi | 43% | 1906 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 56,449 psi | 85% | 3146 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 52,808 psi | 79% | 3117 fps | 99.4% |
| IMR 7828 SSC | <<locked>> | 80% | 52,446 psi | 79% | 3192 fps | 99.6% |
| IMR 7977 Enduron | <<locked>> | 88% | 54,955 psi | 82% | 3117 fps | 95.3% |
| IMR 8133 Enduron | <<locked>> | 80% | 33,866 psi | 51% | 2785 fps | 95.4% |
| Lovex S071 | <<locked>> | 80% | 45,165 psi | 68% | 2943 fps | 100% |
| Norma 217 | <<locked>> | 80% | 34,534 psi | 52% | 2818 fps | 97.9% |
| Norma MRP | <<locked>> | 80% | 54,955 psi | 82% | 3228 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 50,285 psi | 75% | 3104 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,602 psi | 44% | 1952 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 43,482 psi | 65% | 3074 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 40,611 psi | 61% | 2963 fps | 96.5% |
| Rottweil R 904 | <<locked>> | 80% | 55,187 psi | 83% | 3163 fps | 99.8% |
| Rottweil R 905 | <<locked>> | 80% | 54,752 psi | 82% | 3182 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 94% | 46,572 psi | 70% | 3028 fps | 95.4% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 54,404 psi | 82% | 3176 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 56,507 psi | 85% | 3146 fps | 99.7% |
| Somchem S385 | <<locked>> | 80% | 55,216 psi | 83% | 3146 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 48,631 psi | 73% | 3018 fps | 99.9% |
| Vihtavuori N170 | <<locked>> | 84% | 48,370 psi | 73% | 3035 fps | 95.2% |
| Vihtavuori N555 | <<locked>> | 80% | 55,434 psi | 83% | 3156 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 54,128 psi | 81% | 3228 fps | 99.6% |
| Vihtavuori N565 | <<locked>> | 80% | 46,383 psi | 70% | 3051 fps | 98.6% |
| Vihtavuori N568 | <<locked>> | 80% | 41,379 psi | 62% | 2976 fps | 96.2% |
| Vihtavuori N570 | 90.4 gr | 84% | 45,310 psi | 68% | 3104 fps | 95.4% |
| Winchester StaBALL HD | <<locked>> | 80% | 50,662 psi | 76% | 3159 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 55,564 psi | 83% | 3153 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 57 powders for 7.21 Firebird loaded with the .284 | 140gr | Barnes X BT. ADI AR 2218 delivers the highest muzzle velocity at 3,399 fps; across all powders the maximum-charge window runs from 2,126 fps to 3,399 fps. Accurate 8700 gives the best case fill at 100 %, and 57 of the 57 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 1:10.5 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. Hodgdon Retumbo, ADI AR 2218, Vihtavuori N570 rank at the top here: for 7.21 Firebird with the .284 | 140gr | Barnes X BT 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.