Load Specifications
Load data in caliber 7.21 Firebird with .284 | 165gr | Osprey Virtus bullet and 55 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2218, Ramshot LRT and Hodgdon Retumbo.
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% | 57,334 psi | 86% | 2959 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 54,288 psi | 81% | 3025 fps | 98.9% |
| Accurate MAGPRO | <<locked>> | 82% | 57,000 psi | 85% | 3087 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 58,508 psi | 88% | 3054 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 57,537 psi | 86% | 3077 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 57,479 psi | 86% | 3064 fps | 100% |
| ADI AR 2218 | <<locked>> | 96% | 58,508 psi | 88% | 3215 fps | 99.8% |
| ADI AR 2225 | <<locked>> | 94% | 57,435 psi | 86% | 3087 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 57,928 psi | 87% | 3041 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 57,943 psi | 87% | 3068 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 60,205 psi | 90% | 3018 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 57,435 psi | 86% | 3048 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 56,086 psi | 84% | 3110 fps | 99.4% |
| Alliant Reloder-50 | <<locked>> | 96% | 56,260 psi | 84% | 3107 fps | 99.1% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 57,682 psi | 86% | 3045 fps | 99.6% |
| Bofors RP15 | <<locked>> | 86% | 57,537 psi | 86% | 3064 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 57,276 psi | 86% | 3077 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 57,943 psi | 87% | 3068 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 58,914 psi | 88% | 3084 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 59,915 psi | 90% | 3068 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 84% | 58,726 psi | 88% | 3048 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 57,580 psi | 86% | 3153 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,029 psi | 57% | 1962 fps | 100% |
| Hodgdon US 869ᴾ | <<locked>> | 100% | 59,016 psi | 88% | 3091 fps | 96.4% |
| IMR 4955 Enduron | <<locked>> | 84% | 59,640 psi | 89% | 3038 fps | 100% |
| IMR 7828 SSC | <<locked>> | 86% | 60,336 psi | 90% | 3127 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 58,349 psi | 87% | 2999 fps | 97.5% |
| IMR 8133 Enduron | <<locked>> | 98% | 59,973 psi | 90% | 3133 fps | 100% |
| Lovex D100 | <<locked>> | 94% | 60,249 psi | 90% | 3058 fps | 97% |
| Lovex S071 | <<locked>> | 90% | 59,509 psi | 89% | 2989 fps | 100% |
| Norma 217 | <<locked>> | 96% | 57,754 psi | 87% | 3094 fps | 100% |
| Norma MRP | <<locked>> | 82% | 58,349 psi | 87% | 3081 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 57,798 psi | 87% | 3087 fps | 100% |
| Ramshot LRT | <<locked>> | 96% | 57,885 psi | 87% | 3133 fps | 96.3% |
| Ramshot Magnum | <<locked>> | 86% | 56,289 psi | 84% | 3009 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,146 psi | 59% | 2008 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 58,494 psi | 88% | 3133 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 57,276 psi | 86% | 3110 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 58,537 psi | 88% | 3022 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 57,870 psi | 87% | 3035 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 94% | 60,249 psi | 90% | 3058 fps | 97% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 55,738 psi | 84% | 3028 fps | 98.8% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 57,508 psi | 86% | 3031 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 60,046 psi | 90% | 3015 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 57,957 psi | 87% | 2999 fps | 100% |
| Vihtavuori 24N41 | <<locked>> | 98% | 60,017 psi | 90% | 3107 fps | 96.5% |
| Vihtavuori N165 | <<locked>> | 86% | 58,320 psi | 87% | 2989 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 57,885 psi | 87% | 3035 fps | 98.6% |
| Vihtavuori N555 | <<locked>> | 82% | 57,682 psi | 86% | 2992 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 57,595 psi | 86% | 3094 fps | 100% |
| Vihtavuori N565 | <<locked>> | 88% | 59,103 psi | 89% | 3091 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 57,566 psi | 86% | 3114 fps | 99.9% |
| Vihtavuori N570 | <<locked>> | 92% | 59,393 psi | 89% | 3189 fps | 99.5% |
| Winchester StaBALL HD | <<locked>> | 84% | 58,030 psi | 87% | 3061 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 57,957 psi | 87% | 2999 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% | 50,183 psi | 75% | 2851 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 40,074 psi | 60% | 2753 fps | 95.3% |
| Accurate MAGPRO | <<locked>> | 80% | 53,069 psi | 80% | 3022 fps | 99.8% |
| ADI AR 2209 | <<locked>> | 80% | 54,636 psi | 82% | 2995 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 49,980 psi | 75% | 2953 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 37,304 psi | 56% | 2694 fps | 98.3% |
| ADI AR 2218 | 91.1 gr | 86% | 39,885 psi | 60% | 2835 fps | 95.8% |
| ADI AR 2225 | <<locked>> | 80% | 34,592 psi | 52% | 2664 fps | 99.7% |
| Alliant Reloder-19 | <<locked>> | 80% | 54,404 psi | 82% | 2989 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 50,589 psi | 76% | 2949 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 49,255 psi | 74% | 2861 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 43,468 psi | 65% | 2822 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 38,348 psi | 57% | 2753 fps | 95% |
| Alliant Reloder-50 | <<locked>> | 88% | 41,481 psi | 62% | 2818 fps | 95.7% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 47,268 psi | 71% | 2861 fps | 98.1% |
| Bofors RP15 | <<locked>> | 80% | 47,094 psi | 71% | 2887 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 40,538 psi | 61% | 2772 fps | 99% |
| Bofors RP5 | <<locked>> | 80% | 50,589 psi | 76% | 2949 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 40,727 psi | 61% | 2772 fps | 99.4% |
| Hodgdon H4831 | <<locked>> | 80% | 52,127 psi | 78% | 2943 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 80% | 51,242 psi | 77% | 2930 fps | 99.8% |
| Hodgdon Retumbo | 80 gr | 80% | 42,801 psi | 64% | 2897 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,558 psi | 43% | 1759 fps | 100% |
| Hodgdon US 869 | <<locked>> | 98% | 54,926 psi | 82% | 3022 fps | 95.4% |
| IMR 4955 Enduron | <<locked>> | 80% | 52,388 psi | 79% | 2923 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 48,820 psi | 73% | 2940 fps | 99.8% |
| IMR 7977 Enduron | <<locked>> | 84% | 47,935 psi | 72% | 2818 fps | 95.1% |
| IMR 8133 Enduron | <<locked>> | 80% | 31,995 psi | 48% | 2575 fps | 96.1% |
| Lovex D100 | <<locked>> | 90% | 52,069 psi | 78% | 2923 fps | 95.2% |
| Lovex S071 | <<locked>> | 80% | 43,047 psi | 65% | 2726 fps | 100% |
| Norma 217 | <<locked>> | 80% | 32,503 psi | 49% | 2602 fps | 98.4% |
| Norma MRP | <<locked>> | 80% | 54,302 psi | 81% | 3022 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 49,763 psi | 75% | 2959 fps | 100% |
| Ramshot LRT | 99.4 gr | 94% | 53,809 psi | 81% | 3064 fps | 95.3% |
| Ramshot Magnum | <<locked>> | 80% | 44,875 psi | 67% | 2825 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,341 psi | 44% | 1798 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 42,583 psi | 64% | 2867 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 38,928 psi | 58% | 2759 fps | 97.5% |
| Rottweil R 904 | <<locked>> | 80% | 54,795 psi | 82% | 2966 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 54,259 psi | 81% | 2979 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 52,069 psi | 78% | 2923 fps | 95.2% |
| SNPE Vectan SP 13 | <<locked>> | 92% | 42,105 psi | 63% | 2776 fps | 95.6% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 53,911 psi | 81% | 2976 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 55,985 psi | 84% | 2956 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 54,259 psi | 81% | 2943 fps | 100% |
| Vihtavuori 24N41 | <<locked>> | 96% | 55,796 psi | 84% | 3038 fps | 95.5% |
| Vihtavuori N165 | <<locked>> | 80% | 47,848 psi | 72% | 2825 fps | 100% |
| Vihtavuori N170 | <<locked>> | 82% | 43,932 psi | 66% | 2782 fps | 95.5% |
| Vihtavuori N555 | <<locked>> | 80% | 54,099 psi | 81% | 2940 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 53,650 psi | 80% | 3028 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 80% | 44,759 psi | 67% | 2844 fps | 99.3% |
| Vihtavuori N568 | <<locked>> | 80% | 39,871 psi | 60% | 2776 fps | 97.2% |
| Vihtavuori N570 | <<locked>> | 82% | 41,060 psi | 62% | 2838 fps | 95.6% |
| Winchester StaBALL HD | <<locked>> | 80% | 49,734 psi | 75% | 2943 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 50,531 psi | 76% | 2884 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 | 165gr | Osprey Virtus. ADI AR 2218 delivers the highest muzzle velocity at 3,215 fps; across all powders the maximum-charge window runs from 1,962 fps to 3,215 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 165.0 gr projectile in 0.284" calls for a 1:8.5 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. ADI AR 2218, Ramshot LRT, Hodgdon Retumbo rank at the top here: for 7.21 Firebird with the .284 | 165gr | Osprey Virtus 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.