Load Specifications
Load data in caliber 7.21 Firebird with .284 | 139gr | Hornady InterBond bullet and 53 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>> | 86% | 58,378 psi | 88% | 3189 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 50,343 psi | 75% | 3143 fps | 96.8% |
| Accurate High Country | <<locked>> | 82% | 56,405 psi | 85% | 3297 fps | 99.9% |
| Accurate MAGPRO | <<locked>> | 84% | 57,624 psi | 86% | 3307 fps | 99.6% |
| ADI AR 2209 | <<locked>> | 84% | 59,059 psi | 89% | 3284 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 58,001 psi | 87% | 3301 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 94% | 57,595 psi | 86% | 3281 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 58,523 psi | 88% | 3412 fps | 99.1% |
| ADI AR 2225 | <<locked>> | 96% | 57,159 psi | 86% | 3301 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 58,653 psi | 88% | 3271 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 58,508 psi | 88% | 3294 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 56,637 psi | 85% | 3189 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 57,624 psi | 86% | 3274 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 57,725 psi | 87% | 3284 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 56,347 psi | 84% | 3314 fps | 98.5% |
| Alliant Reloder-50 | <<locked>> | 98% | 56,710 psi | 85% | 3304 fps | 98.1% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 58,349 psi | 87% | 3255 fps | 98.9% |
| Bofors RP15 | <<locked>> | 88% | 57,885 psi | 87% | 3284 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 57,624 psi | 86% | 3294 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 58,508 psi | 88% | 3294 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 59,103 psi | 89% | 3301 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 56,623 psi | 85% | 3225 fps | 99.7% |
| Hodgdon H4831 SC | <<locked>> | 86% | 59,451 psi | 89% | 3271 fps | 99.8% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 59,234 psi | 89% | 3176 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 57,188 psi | 86% | 3369 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,913 psi | 57% | 2129 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 56,652 psi | 85% | 3202 fps | 99.7% |
| IMR 7828 SSC | <<locked>> | 86% | 56,478 psi | 85% | 3281 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 92% | 59,146 psi | 89% | 3205 fps | 96.1% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 60,118 psi | 90% | 3346 fps | 100% |
| Lovex S071 | <<locked>> | 92% | 60,307 psi | 90% | 3215 fps | 100% |
| Norma 217 | <<locked>> | 98% | 57,595 psi | 86% | 3304 fps | 100% |
| Norma MRP | <<locked>> | 84% | 58,914 psi | 88% | 3310 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 58,059 psi | 87% | 3310 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 56,797 psi | 85% | 3228 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,972 psi | 58% | 2178 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 58,523 psi | 88% | 3353 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 57,595 psi | 86% | 3317 fps | 99.7% |
| Rottweil R 904 | <<locked>> | 84% | 59,364 psi | 89% | 3248 fps | 100% |
| Rottweil R 905 | <<locked>> | 84% | 58,494 psi | 88% | 3261 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 52,315 psi | 78% | 3156 fps | 96.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 58,102 psi | 87% | 3258 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 57,159 psi | 86% | 3176 fps | 99.7% |
| Somchem S385 | <<locked>> | 84% | 58,755 psi | 88% | 3225 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 58,972 psi | 88% | 3212 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 58,682 psi | 88% | 3241 fps | 97.5% |
| Vihtavuori N555 | <<locked>> | 84% | 58,392 psi | 88% | 3225 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 58,160 psi | 87% | 3317 fps | 99.8% |
| Vihtavuori N565 | <<locked>> | 90% | 59,582 psi | 89% | 3310 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 92% | 57,783 psi | 87% | 3323 fps | 99.5% |
| Vihtavuori N570 | <<locked>> | 94% | 59,335 psi | 89% | 3396 fps | 98.6% |
| Winchester StaBALL HD | <<locked>> | 86% | 58,001 psi | 87% | 3291 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 58,856 psi | 88% | 3225 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% | 47,616 psi | 71% | 3012 fps | 100% |
| Accurate 8700 | <<locked>> | 98% | 46,586 psi | 70% | 3064 fps | 95.7% |
| Accurate High Country | <<locked>> | 80% | 52,634 psi | 79% | 3228 fps | 99.6% |
| Accurate MAGPRO | <<locked>> | 80% | 49,908 psi | 75% | 3166 fps | 98.6% |
| ADI AR 2209 | <<locked>> | 80% | 51,605 psi | 77% | 3156 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 47,007 psi | 70% | 3100 fps | 98.8% |
| ADI AR 2217 | <<locked>> | 80% | 35,056 psi | 53% | 2812 fps | 95.8% |
| ADI AR 2218 | 98.9 gr | 90% | 43,265 psi | 65% | 3091 fps | 95% |
| ADI AR 2225 | <<locked>> | 80% | 32,387 psi | 49% | 2779 fps | 97.8% |
| Alliant Reloder-19 | <<locked>> | 80% | 51,488 psi | 77% | 3146 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 47,776 psi | 72% | 3104 fps | 99.6% |
| Alliant Reloder-23 | <<locked>> | 80% | 46,456 psi | 70% | 3025 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 40,596 psi | 61% | 2966 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 53,592 psi | 80% | 3219 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 88% | 44,860 psi | 67% | 3084 fps | 95.6% |
| Alliant Reloder-50 | <<locked>> | 92% | 45,150 psi | 68% | 3077 fps | 95.1% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 44,817 psi | 67% | 2999 fps | 96% |
| Bofors RP15 | <<locked>> | 80% | 44,440 psi | 67% | 3031 fps | 99.1% |
| Bofors RP30 | <<locked>> | 80% | 37,985 psi | 57% | 2897 fps | 97% |
| Bofors RP5 | <<locked>> | 80% | 47,776 psi | 72% | 3104 fps | 99.6% |
| Hodgdon H1000 | <<locked>> | 80% | 38,218 psi | 57% | 2897 fps | 97.7% |
| Hodgdon H4831 | <<locked>> | 80% | 49,327 psi | 74% | 3094 fps | 98.8% |
| Hodgdon H4831 SC | <<locked>> | 80% | 48,544 psi | 73% | 3081 fps | 98.7% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 55,506 psi | 83% | 3123 fps | 100% |
| Hodgdon Retumbo | 83 gr | 80% | 39,668 psi | 59% | 3022 fps | 99% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,427 psi | 43% | 1909 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 49,850 psi | 75% | 3077 fps | 99% |
| IMR 7828 SSC | <<locked>> | 80% | 45,701 psi | 69% | 3081 fps | 98.6% |
| IMR 7977 Enduron | <<locked>> | 90% | 55,506 psi | 83% | 3143 fps | 95.3% |
| IMR 8133 Enduron | <<locked>> | 84% | 34,519 psi | 52% | 2818 fps | 95.4% |
| Lovex S071 | <<locked>> | 80% | 41,017 psi | 61% | 2881 fps | 99.8% |
| Norma 217 | <<locked>> | 80% | 30,240 psi | 45% | 2713 fps | 95.7% |
| Norma MRP | <<locked>> | 80% | 51,140 psi | 77% | 3179 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 46,311 psi | 69% | 3094 fps | 99% |
| Ramshot Magnum | <<locked>> | 80% | 41,814 psi | 63% | 2956 fps | 99.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,283 psi | 44% | 1955 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 39,334 psi | 59% | 2995 fps | 99.6% |
| ReloadSwiss RS 80 | <<locked>> | 82% | 39,218 psi | 59% | 2946 fps | 95.8% |
| Rottweil R 904 | <<locked>> | 80% | 52,054 psi | 78% | 3127 fps | 99.5% |
| Rottweil R 905 | <<locked>> | 80% | 51,140 psi | 77% | 3136 fps | 99.9% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 48,617 psi | 73% | 3084 fps | 95.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 50,792 psi | 76% | 3133 fps | 99.8% |
| Somchem S361 | <<locked>> | 80% | 53,417 psi | 80% | 3110 fps | 99.3% |
| Somchem S385 | <<locked>> | 80% | 51,605 psi | 77% | 3107 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 45,266 psi | 68% | 2976 fps | 99.6% |
| Vihtavuori N170 | <<locked>> | 88% | 51,213 psi | 77% | 3107 fps | 95.9% |
| Vihtavuori N555 | <<locked>> | 80% | 51,285 psi | 77% | 3110 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 50,560 psi | 76% | 3179 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 80% | 42,221 psi | 63% | 2979 fps | 97.5% |
| Vihtavuori N568 | <<locked>> | 82% | 40,205 psi | 60% | 2966 fps | 95.6% |
| Vihtavuori N570 | 94.8 gr | 88% | 47,776 psi | 72% | 3173 fps | 96% |
| Winchester StaBALL HD | <<locked>> | 80% | 46,137 psi | 69% | 3100 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 47,834 psi | 72% | 3038 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 53 powders for 7.21 Firebird loaded with the .284 | 139gr | Hornady InterBond. ADI AR 2218 delivers the highest muzzle velocity at 3,412 fps; across all powders the maximum-charge window runs from 2,129 fps to 3,412 fps. Accurate 8700 gives the best case fill at 100 %, and 53 of the 53 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 139.0 gr projectile in 0.284" calls for a 1:10.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, IMR 8133 Enduron 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 | 139gr | Hornady InterBond 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.