Load Specifications
Load data in caliber 7.21 Firebird with .284 | 156gr | Lapua Naturalis 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, Vihtavuori N570 and IMR 8133 Enduron.
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% | 60,176 psi | 90% | 3068 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 56,869 psi | 85% | 3127 fps | 98.9% |
| Accurate MAGPRO | <<locked>> | 82% | 59,350 psi | 89% | 3192 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 60,133 psi | 90% | 3150 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 59,509 psi | 89% | 3179 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 59,567 psi | 89% | 3169 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 56,463 psi | 85% | 3245 fps | 99.5% |
| ADI AR 2225 | <<locked>> | 94% | 59,640 psi | 89% | 3189 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 59,828 psi | 90% | 3143 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 60,220 psi | 90% | 3173 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 58,595 psi | 88% | 3068 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 59,654 psi | 89% | 3150 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 58,827 psi | 88% | 3222 fps | 99.4% |
| Alliant Reloder-50 | <<locked>> | 96% | 59,770 psi | 90% | 3225 fps | 99.3% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 58,987 psi | 88% | 3130 fps | 99.5% |
| Bofors RP15 | <<locked>> | 86% | 59,640 psi | 89% | 3166 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 59,683 psi | 89% | 3182 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 60,220 psi | 90% | 3173 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 56,826 psi | 85% | 3123 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 57,667 psi | 86% | 3100 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 56,753 psi | 85% | 3087 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 88% | 59,727 psi | 90% | 3258 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,189 psi | 57% | 2024 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,450 psi | 86% | 3074 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 58,218 psi | 87% | 3166 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 59,915 psi | 90% | 3091 fps | 97.3% |
| IMR 8133 Enduron | <<locked>> | 96% | 58,726 psi | 88% | 3182 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 58,218 psi | 87% | 3087 fps | 96.1% |
| Lovex S071 | <<locked>> | 88% | 58,668 psi | 88% | 3045 fps | 100% |
| Norma 217 | <<locked>> | 94% | 56,811 psi | 85% | 3150 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 60,060 psi | 90% | 3192 fps | 100% |
| Ramshot LRT | <<locked>> | 96% | 59,915 psi | 90% | 3232 fps | 96.2% |
| Ramshot Magnum | <<locked>> | 86% | 58,595 psi | 88% | 3110 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,334 psi | 59% | 2073 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 56,521 psi | 85% | 3179 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 60,017 psi | 90% | 3219 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 60,176 psi | 90% | 3117 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 59,843 psi | 90% | 3136 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 58,218 psi | 87% | 3087 fps | 96.1% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 58,305 psi | 87% | 3130 fps | 98.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,466 psi | 89% | 3130 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 60,234 psi | 90% | 3100 fps | 100% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 52,025 psi | 78% | 3045 fps | 96.3% |
| Vihtavuori N165 | <<locked>> | 84% | 56,623 psi | 85% | 3035 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 60,191 psi | 90% | 3133 fps | 98.6% |
| Vihtavuori N555 | <<locked>> | 82% | 60,234 psi | 90% | 3097 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 59,582 psi | 89% | 3196 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 57,696 psi | 86% | 3136 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 60,031 psi | 90% | 3219 fps | 99.9% |
| Vihtavuori N570 | <<locked>> | 90% | 57,638 psi | 86% | 3228 fps | 99.1% |
| Winchester StaBALL HD | <<locked>> | 82% | 56,521 psi | 85% | 3114 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 60,060 psi | 90% | 3097 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% | 52,866 psi | 79% | 2959 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 42,656 psi | 64% | 2864 fps | 95.6% |
| Accurate MAGPRO | <<locked>> | 80% | 55,390 psi | 83% | 3130 fps | 99.8% |
| ADI AR 2209 | <<locked>> | 80% | 56,391 psi | 85% | 3094 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 51,822 psi | 78% | 3054 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 39,465 psi | 59% | 2802 fps | 98.5% |
| ADI AR 2218 | 93.4 gr | 86% | 42,221 psi | 63% | 2949 fps | 96.1% |
| ADI AR 2225 | <<locked>> | 80% | 36,912 psi | 55% | 2782 fps | 99.8% |
| Alliant Reloder-19 | <<locked>> | 80% | 56,028 psi | 84% | 3084 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 52,707 psi | 79% | 3051 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 51,576 psi | 77% | 2966 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 45,730 psi | 69% | 2930 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 41,002 psi | 61% | 2874 fps | 95.5% |
| Alliant Reloder-50 | <<locked>> | 86% | 41,829 psi | 63% | 2881 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 48,762 psi | 73% | 2953 fps | 98% |
| Bofors RP15 | <<locked>> | 80% | 49,327 psi | 74% | 2992 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 42,931 psi | 64% | 2884 fps | 99.1% |
| Bofors RP5 | <<locked>> | 80% | 52,707 psi | 79% | 3051 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 42,786 psi | 64% | 2874 fps | 99.5% |
| Hodgdon H4831 | <<locked>> | 80% | 54,085 psi | 81% | 3045 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 80% | 53,040 psi | 80% | 3028 fps | 99.7% |
| Hodgdon Retumbo | <<locked>> | 80% | 45,049 psi | 68% | 3009 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,848 psi | 43% | 1818 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 54,041 psi | 81% | 3018 fps | 99.8% |
| IMR 7828 SSC | <<locked>> | 80% | 50,807 psi | 76% | 3041 fps | 99.8% |
| IMR 7977 Enduron | <<locked>> | 84% | 49,632 psi | 74% | 2910 fps | 95% |
| IMR 8133 Enduron | 79.8 gr | 80% | 34,693 psi | 52% | 2703 fps | 96.8% |
| Lovex D100 | <<locked>> | 90% | 54,288 psi | 81% | 3022 fps | 95.1% |
| Lovex S071 | <<locked>> | 80% | 45,919 psi | 69% | 2841 fps | 100% |
| Norma 217 | <<locked>> | 80% | 35,360 psi | 53% | 2733 fps | 98.9% |
| Ramshot Grand | <<locked>> | 80% | 52,025 psi | 78% | 3064 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 55,970 psi | 84% | 3166 fps | 95.2% |
| Ramshot Magnum | <<locked>> | 80% | 47,311 psi | 71% | 2933 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,660 psi | 44% | 1860 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 45,179 psi | 68% | 2986 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 41,800 psi | 63% | 2884 fps | 97.8% |
| Rottweil R 904 | <<locked>> | 80% | 56,507 psi | 85% | 3061 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 56,130 psi | 84% | 3081 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 54,288 psi | 81% | 3022 fps | 95.1% |
| SNPE Vectan SP 13 | <<locked>> | 92% | 44,744 psi | 67% | 2887 fps | 95.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 55,782 psi | 84% | 3074 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 56,478 psi | 85% | 3045 fps | 100% |
| Vihtavuori 20N29 | <<locked>> | 98% | 48,414 psi | 73% | 2976 fps | 95.2% |
| Vihtavuori N165 | <<locked>> | 80% | 49,777 psi | 75% | 2923 fps | 100% |
| Vihtavuori N170 | <<locked>> | 82% | 46,325 psi | 69% | 2887 fps | 95.7% |
| Vihtavuori N555 | <<locked>> | 80% | 56,797 psi | 85% | 3048 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 55,753 psi | 84% | 3133 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 80% | 47,485 psi | 71% | 2959 fps | 99.4% |
| Vihtavuori N568 | <<locked>> | 80% | 42,424 psi | 64% | 2894 fps | 97.5% |
| Vihtavuori N570 | 87.2 gr | 82% | 43,569 psi | 65% | 2953 fps | 95.9% |
| Winchester StaBALL HD | <<locked>> | 80% | 52,562 psi | 79% | 3058 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 52,504 psi | 79% | 2982 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 55 powders for 7.21 Firebird loaded with the .284 | 156gr | Lapua Naturalis. Hodgdon Retumbo delivers the highest muzzle velocity at 3,258 fps; across all powders the maximum-charge window runs from 2,024 fps to 3,258 fps. Accurate 8700 gives the best case fill at 100 %, and 55 of the 55 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 155.0 gr projectile in 0.284" calls for a 1:10.0 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, 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, Vihtavuori N570, IMR 8133 Enduron rank at the top here: for 7.21 Firebird with the .284 | 156gr | Lapua Naturalis they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG 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.