Load Specifications
Load data in caliber 7.21 Firebird with .284 | 145gr | Prvi Partizan SP 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, 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>> | 84% | 57,232 psi | 86% | 3114 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 54,012 psi | 81% | 3156 fps | 98% |
| Accurate MAGPRO | <<locked>> | 82% | 56,594 psi | 85% | 3235 fps | 99.7% |
| ADI AR 2209 | <<locked>> | 82% | 58,015 psi | 87% | 3209 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 57,043 psi | 86% | 3228 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 56,840 psi | 85% | 3212 fps | 100% |
| ADI AR 2218 | <<locked>> | 96% | 58,059 psi | 87% | 3353 fps | 99.4% |
| ADI AR 2225 | <<locked>> | 94% | 56,884 psi | 85% | 3238 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 57,464 psi | 86% | 3196 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 57,609 psi | 86% | 3222 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 59,741 psi | 90% | 3176 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 56,884 psi | 85% | 3202 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 60,350 psi | 90% | 3327 fps | 99.3% |
| Alliant Reloder-50 | <<locked>> | 96% | 56,318 psi | 84% | 3245 fps | 98.4% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 57,188 psi | 86% | 3186 fps | 99% |
| Bofors RP15 | <<locked>> | 86% | 57,188 psi | 86% | 3215 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 56,985 psi | 85% | 3228 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 57,609 psi | 86% | 3222 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 58,305 psi | 87% | 3232 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 59,451 psi | 89% | 3219 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 84% | 58,334 psi | 87% | 3199 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 88% | 56,724 psi | 85% | 3301 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,072 psi | 57% | 2096 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 59,205 psi | 89% | 3189 fps | 100% |
| IMR 7828 SSC | <<locked>> | 86% | 59,640 psi | 89% | 3278 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 57,943 psi | 87% | 3140 fps | 96.5% |
| IMR 8133 Enduron | <<locked>> | 98% | 59,625 psi | 89% | 3281 fps | 100% |
| Lovex S071 | <<locked>> | 90% | 59,466 psi | 89% | 3146 fps | 100% |
| Norma 217 | <<locked>> | 96% | 57,348 psi | 86% | 3241 fps | 100% |
| Norma MRP | <<locked>> | 82% | 57,928 psi | 87% | 3235 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 57,261 psi | 86% | 3238 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 60,162 psi | 90% | 3222 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,131 psi | 59% | 2146 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 57,885 psi | 87% | 3284 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 56,985 psi | 85% | 3251 fps | 99.8% |
| Rottweil R 904 | <<locked>> | 82% | 58,001 psi | 87% | 3176 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 57,493 psi | 86% | 3192 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 55,651 psi | 83% | 3166 fps | 98% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 57,130 psi | 86% | 3186 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 59,669 psi | 89% | 3166 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 57,769 psi | 87% | 3153 fps | 100% |
| Vihtavuori N165 | <<locked>> | 86% | 57,885 psi | 87% | 3140 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 57,711 psi | 87% | 3176 fps | 97.8% |
| Vihtavuori N555 | <<locked>> | 82% | 57,435 psi | 86% | 3150 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 57,116 psi | 86% | 3241 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 88% | 58,871 psi | 88% | 3241 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 57,188 psi | 86% | 3258 fps | 99.6% |
| Vihtavuori N570 | <<locked>> | 92% | 58,929 psi | 88% | 3333 fps | 98.9% |
| Winchester StaBALL HD | <<locked>> | 84% | 57,363 psi | 86% | 3215 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 57,725 psi | 87% | 3153 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% | 50,024 psi | 75% | 3002 fps | 100% |
| Accurate 8700 | <<locked>> | 94% | 43,105 psi | 65% | 2946 fps | 95.1% |
| Accurate MAGPRO | <<locked>> | 80% | 52,605 psi | 79% | 3163 fps | 99.3% |
| ADI AR 2209 | <<locked>> | 80% | 54,215 psi | 81% | 3146 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 49,472 psi | 74% | 3097 fps | 99.5% |
| ADI AR 2217 | <<locked>> | 80% | 37,086 psi | 56% | 2818 fps | 97.2% |
| ADI AR 2218 | 98.7 gr | 88% | 42,844 psi | 64% | 3035 fps | 95.5% |
| ADI AR 2225 | <<locked>> | 80% | 34,490 psi | 52% | 2789 fps | 99% |
| Alliant Reloder-19 | <<locked>> | 80% | 53,853 psi | 81% | 3136 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 50,227 psi | 75% | 3094 fps | 99.9% |
| Alliant Reloder-23 | <<locked>> | 80% | 48,994 psi | 73% | 3012 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 43,207 psi | 65% | 2966 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 86% | 44,512 psi | 67% | 3025 fps | 96% |
| Alliant Reloder-50 | <<locked>> | 90% | 44,991 psi | 67% | 3022 fps | 95.6% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 46,847 psi | 70% | 2992 fps | 97.1% |
| Bofors RP15 | <<locked>> | 80% | 46,789 psi | 70% | 3028 fps | 99.6% |
| Bofors RP30 | <<locked>> | 80% | 40,306 psi | 60% | 2900 fps | 98.1% |
| Bofors RP5 | <<locked>> | 80% | 50,227 psi | 75% | 3094 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 80% | 40,408 psi | 61% | 2904 fps | 98.7% |
| Hodgdon H4831 | <<locked>> | 80% | 51,793 psi | 78% | 3091 fps | 99.4% |
| Hodgdon H4831 SC | <<locked>> | 80% | 50,807 psi | 76% | 3071 fps | 99.3% |
| Hodgdon Retumbo | 84.7 gr | 80% | 42,380 psi | 64% | 3031 fps | 99.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,601 psi | 43% | 1883 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 52,098 psi | 78% | 3068 fps | 99.5% |
| IMR 7828 SSC | <<locked>> | 80% | 48,370 psi | 73% | 3081 fps | 99.4% |
| IMR 7977 Enduron | <<locked>> | 88% | 54,259 psi | 81% | 3074 fps | 95.6% |
| IMR 8133 Enduron | <<locked>> | 82% | 34,447 psi | 52% | 2766 fps | 95.9% |
| Lovex S071 | <<locked>> | 80% | 43,105 psi | 65% | 2871 fps | 100% |
| Norma 217 | <<locked>> | 80% | 32,503 psi | 49% | 2726 fps | 97.3% |
| Norma MRP | <<locked>> | 80% | 53,969 psi | 81% | 3173 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 49,385 psi | 74% | 3100 fps | 99.7% |
| Ramshot Magnum | <<locked>> | 80% | 44,585 psi | 67% | 2959 fps | 99.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,356 psi | 44% | 1926 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 42,177 psi | 63% | 3002 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 38,928 psi | 58% | 2887 fps | 96.2% |
| Rottweil R 904 | <<locked>> | 80% | 54,331 psi | 81% | 3114 fps | 99.9% |
| Rottweil R 905 | <<locked>> | 80% | 53,780 psi | 81% | 3130 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 94% | 45,078 psi | 68% | 2963 fps | 95.3% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 53,432 psi | 80% | 3127 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 55,709 psi | 84% | 3100 fps | 99.8% |
| Somchem S385 | <<locked>> | 80% | 53,969 psi | 81% | 3094 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 47,471 psi | 71% | 2966 fps | 99.9% |
| Vihtavuori N170 | <<locked>> | 84% | 47,007 psi | 70% | 2976 fps | 95.3% |
| Vihtavuori N555 | <<locked>> | 80% | 53,925 psi | 81% | 3097 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 53,258 psi | 80% | 3176 fps | 99.6% |
| Vihtavuori N565 | <<locked>> | 80% | 44,686 psi | 67% | 2982 fps | 98.5% |
| Vihtavuori N568 | <<locked>> | 80% | 39,726 psi | 60% | 2900 fps | 95.9% |
| Vihtavuori N570 | 92.3 gr | 84% | 44,034 psi | 66% | 3038 fps | 95.3% |
| Winchester StaBALL HD | <<locked>> | 80% | 49,414 psi | 74% | 3094 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 50,082 psi | 75% | 3028 fps | 99.9% |
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 50 powders for 7.21 Firebird loaded with the .284 | 145gr | Prvi Partizan SP. ADI AR 2218 delivers the highest muzzle velocity at 3,353 fps; across all powders the maximum-charge window runs from 2,096 fps to 3,353 fps. Accurate 8700 gives the best case fill at 100 %, and 50 of the 50 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 145.0 gr projectile in 0.284" calls for a 1:13.0 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, ReloadSwiss RS 14 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 | 145gr | Prvi Partizan SP 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.