Load Specifications
Load data in caliber 7.21 Firebird with .284 | 139gr | Barnes LRX BT bullet and 53 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Vihtavuori N570, Hodgdon Retumbo and ReloadSwiss RS 76.
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>> | 88% | 59,683 psi | 89% | 3209 fps | 100% |
| Accurate MAGPRO | <<locked>> | 86% | 59,263 psi | 89% | 3337 fps | 99.7% |
| ADI AR 2209 | <<locked>> | 84% | 57,116 psi | 86% | 3255 fps | 100% |
| ADI AR 2213 | <<locked>> | 88% | 59,973 psi | 90% | 3333 fps | 100% |
| ADI AR 2217 | <<locked>> | 96% | 59,292 psi | 89% | 3307 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 55,956 psi | 84% | 3369 fps | 98.7% |
| ADI AR 2225 | <<locked>> | 98% | 58,552 psi | 88% | 3327 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 56,724 psi | 85% | 3241 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 88% | 60,278 psi | 90% | 3323 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 88% | 58,247 psi | 87% | 3219 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 92% | 59,146 psi | 89% | 3301 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 84% | 59,466 psi | 89% | 3314 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 96% | 57,856 psi | 87% | 3340 fps | 98.6% |
| Alliant Reloder-50ᴾ | <<locked>> | 100% | 57,740 psi | 87% | 3327 fps | 98.2% |
| Baschieri & Pellagri 109 | <<locked>> | 90% | 60,263 psi | 90% | 3287 fps | 99% |
| Bofors RP15 | <<locked>> | 90% | 59,611 psi | 89% | 3314 fps | 100% |
| Bofors RP30 | <<locked>> | 94% | 58,842 psi | 88% | 3320 fps | 100% |
| Bofors RP5 | <<locked>> | 88% | 60,278 psi | 90% | 3323 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 56,594 psi | 85% | 3268 fps | 100% |
| Hodgdon H4831 | <<locked>> | 86% | 58,508 psi | 88% | 3258 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 86% | 57,551 psi | 86% | 3241 fps | 99.7% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 57,116 psi | 86% | 3150 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 92% | 58,726 psi | 88% | 3399 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,652 psi | 56% | 2119 fps | 100% |
| IMR 4350 | <<locked>> | 82% | 59,030 psi | 88% | 3225 fps | 100% |
| IMR 4831 | <<locked>> | 82% | 59,857 psi | 90% | 3222 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 86% | 58,552 psi | 88% | 3235 fps | 99.8% |
| IMR 7828 SSC | <<locked>> | 88% | 58,291 psi | 87% | 3317 fps | 99.9% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 57,217 psi | 86% | 3307 fps | 100% |
| Lovex S071 | <<locked>> | 92% | 57,682 psi | 86% | 3182 fps | 100% |
| Norma 217ᴾ | <<locked>> | 100% | 58,769 psi | 88% | 3327 fps | 100% |
| Norma MRP | <<locked>> | 84% | 56,492 psi | 85% | 3278 fps | 100% |
| Ramshot Grand | <<locked>> | 88% | 60,191 psi | 90% | 3343 fps | 100% |
| Ramshot Magnum | <<locked>> | 90% | 58,421 psi | 88% | 3255 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,667 psi | 58% | 2169 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 92% | 60,133 psi | 90% | 3386 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 94% | 59,088 psi | 89% | 3346 fps | 99.8% |
| Rottweil R 904 | <<locked>> | 84% | 57,493 psi | 86% | 3222 fps | 99.9% |
| Rottweil R 905 | <<locked>> | 86% | 60,278 psi | 90% | 3291 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 49,603 psi | 74% | 3107 fps | 96% |
| SNPE Vectan Tubal 8000 | <<locked>> | 86% | 59,886 psi | 90% | 3291 fps | 100% |
| Somchem S361 | <<locked>> | 84% | 58,958 psi | 88% | 3205 fps | 99.8% |
| Somchem S365 | <<locked>> | 82% | 59,582 psi | 89% | 3212 fps | 100% |
| Somchem S385 | <<locked>> | 84% | 56,666 psi | 85% | 3196 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 56,811 psi | 85% | 3179 fps | 100% |
| Vihtavuori N170 | <<locked>> | 94% | 60,365 psi | 90% | 3271 fps | 97.7% |
| Vihtavuori N555 | <<locked>> | 86% | 59,814 psi | 90% | 3248 fps | 100% |
| Vihtavuori N560 | <<locked>> | 86% | 59,915 psi | 90% | 3350 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 90% | 57,130 psi | 86% | 3271 fps | 99.8% |
| Vihtavuori N568 | <<locked>> | 94% | 59,335 psi | 89% | 3350 fps | 99.6% |
| Vihtavuori N570 | <<locked>> | 94% | 56,652 psi | 85% | 3350 fps | 98.1% |
| Winchester StaBALL HD | <<locked>> | 88% | 59,509 psi | 89% | 3317 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 56,681 psi | 85% | 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% | 45,252 psi | 68% | 2972 fps | 100% |
| Accurate MAGPRO | <<locked>> | 80% | 47,587 psi | 71% | 3120 fps | 98% |
| ADI AR 2209 | <<locked>> | 80% | 49,806 psi | 75% | 3127 fps | 99.7% |
| ADI AR 2213 | <<locked>> | 80% | 45,020 psi | 67% | 3061 fps | 98.4% |
| ADI AR 2217 | <<locked>> | 82% | 35,723 psi | 54% | 2835 fps | 96% |
| ADI AR 2218 | <<locked>> | 92% | 44,440 psi | 67% | 3120 fps | 95.3% |
| ADI AR 2225 | <<locked>> | 80% | 30,618 psi | 46% | 2726 fps | 96.8% |
| Alliant Reloder-19 | <<locked>> | 80% | 49,545 psi | 74% | 3114 fps | 99.7% |
| Alliant Reloder-22 | <<locked>> | 80% | 45,701 psi | 69% | 3064 fps | 99.3% |
| Alliant Reloder-23 | <<locked>> | 80% | 44,280 psi | 66% | 2989 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 38,609 psi | 58% | 2930 fps | 99.9% |
| Alliant Reloder-26 | <<locked>> | 80% | 50,952 psi | 76% | 3179 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 90% | 45,847 psi | 69% | 3110 fps | 95.8% |
| Alliant Reloder-50 | <<locked>> | 94% | 45,687 psi | 68% | 3091 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 43,134 psi | 65% | 2959 fps | 95.3% |
| Bofors RP15 | <<locked>> | 80% | 42,380 psi | 64% | 2992 fps | 98.6% |
| Bofors RP30 | <<locked>> | 80% | 35,839 psi | 54% | 2848 fps | 96% |
| Bofors RP5 | <<locked>> | 80% | 45,701 psi | 69% | 3064 fps | 99.3% |
| Hodgdon H1000 | <<locked>> | 80% | 36,318 psi | 54% | 2851 fps | 96.9% |
| Hodgdon H4831 | <<locked>> | 80% | 47,456 psi | 71% | 3058 fps | 98.4% |
| Hodgdon H4831 SC | <<locked>> | 80% | 46,659 psi | 70% | 3041 fps | 98.2% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 53,548 psi | 80% | 3097 fps | 100% |
| Hodgdon Retumbo | 81.8 gr | 80% | 37,710 psi | 57% | 2979 fps | 98.4% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,282 psi | 42% | 1903 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 55,361 psi | 83% | 3166 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 56,072 psi | 84% | 3166 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 48,240 psi | 72% | 3051 fps | 98.7% |
| IMR 7828 SSC | <<locked>> | 80% | 43,787 psi | 66% | 3041 fps | 98.1% |
| IMR 8133 Enduron | <<locked>> | 86% | 34,824 psi | 52% | 2831 fps | 95.4% |
| Lovex S071 | <<locked>> | 80% | 38,812 psi | 58% | 2835 fps | 99.5% |
| Norma 217 | <<locked>> | 82% | 30,400 psi | 46% | 2723 fps | 95.7% |
| Norma MRP | <<locked>> | 80% | 48,747 psi | 73% | 3140 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 44,092 psi | 66% | 3054 fps | 98.5% |
| Ramshot Magnum | <<locked>> | 80% | 39,682 psi | 59% | 2910 fps | 98.9% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,979 psi | 43% | 1949 fps | 100% |
| ReloadSwiss RS 76 | 87.5 gr | 80% | 37,173 psi | 56% | 2943 fps | 99.1% |
| ReloadSwiss RS 80 | <<locked>> | 84% | 39,914 psi | 60% | 2969 fps | 96% |
| Rottweil R 904 | <<locked>> | 80% | 50,372 psi | 76% | 3097 fps | 99.3% |
| Rottweil R 905 | <<locked>> | 80% | 49,211 psi | 74% | 3107 fps | 99.7% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 46,267 psi | 69% | 3041 fps | 95% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 48,878 psi | 73% | 3100 fps | 99.7% |
| Somchem S361 | <<locked>> | 80% | 51,474 psi | 77% | 3081 fps | 99.1% |
| Somchem S365 | <<locked>> | 80% | 55,680 psi | 83% | 3156 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 49,501 psi | 74% | 3071 fps | 99.9% |
| Vihtavuori N165 | <<locked>> | 80% | 43,323 psi | 65% | 2936 fps | 99.3% |
| Vihtavuori N170 | <<locked>> | 88% | 48,907 psi | 73% | 3068 fps | 95.1% |
| Vihtavuori N555 | <<locked>> | 80% | 48,907 psi | 73% | 3074 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 48,298 psi | 72% | 3136 fps | 98.6% |
| Vihtavuori N565 | <<locked>> | 80% | 40,016 psi | 60% | 2930 fps | 96.8% |
| Vihtavuori N568 | <<locked>> | 84% | 41,031 psi | 62% | 2989 fps | 95.8% |
| Vihtavuori N570 | 93.3 gr | 88% | 45,208 psi | 68% | 3120 fps | 95.1% |
| Winchester StaBALL HD | <<locked>> | 80% | 43,555 psi | 65% | 3058 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 45,861 psi | 69% | 3002 fps | 99.3% |
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 62 powders for 7.21 Firebird loaded with the .284 | 139gr | Barnes LRX BT. Hodgdon Retumbo delivers the highest muzzle velocity at 3,399 fps; across all powders the maximum-charge window runs from 2,119 fps to 3,399 fps. Accurate 8700 gives the best case fill at 100 %, and 62 of the 62 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (460 MPa), the top charges use 56–90 %, leaving at least 10 % headroom. The 139.0 gr projectile in 0.284" calls for a 1:9.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Alliant Reloder-50, Hodgdon 50BMG 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. Vihtavuori N570, Hodgdon Retumbo, ReloadSwiss RS 76 rank at the top here: for 7.21 Firebird with the .284 | 139gr | Barnes LRX 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.