Load Specifications
Load data in caliber 7.21 Firebird with .284 | 175gr | Speer Grand Slam bullet and 42 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 Ramshot LRT.
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>> | 82% | 59,379 psi | 89% | 2907 fps | 100% |
| Accurate 8700 | <<locked>> | 98% | 57,392 psi | 86% | 2999 fps | 99.6% |
| ADI AR 2213 | <<locked>> | 82% | 59,466 psi | 89% | 3025 fps | 100% |
| ADI AR 2217 | <<locked>> | 90% | 59,988 psi | 90% | 3018 fps | 100% |
| ADI AR 2218 | <<locked>> | 92% | 57,116 psi | 86% | 3110 fps | 99.9% |
| ADI AR 2225 | <<locked>> | 90% | 56,536 psi | 85% | 2989 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 60,017 psi | 90% | 3015 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 82% | 58,334 psi | 87% | 2907 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 86% | 60,002 psi | 90% | 2995 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 90% | 59,379 psi | 89% | 3081 fps | 99.9% |
| Alliant Reloder-50 | <<locked>> | 94% | 60,104 psi | 90% | 3087 fps | 99.8% |
| Baschieri & Pellagri 109 | <<locked>> | 84% | 58,827 psi | 88% | 2986 fps | 99.9% |
| Bofors RP15 | <<locked>> | 84% | 59,582 psi | 89% | 3009 fps | 100% |
| Bofors RP30 | <<locked>> | 88% | 59,857 psi | 90% | 3031 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 60,017 psi | 90% | 3015 fps | 100% |
| Hodgdon H1000 | <<locked>> | 86% | 57,029 psi | 85% | 2972 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 60,307 psi | 90% | 2995 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 84% | 56,507 psi | 85% | 3045 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,290 psi | 57% | 1923 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 57,580 psi | 86% | 2999 fps | 96.9% |
| IMR 7828 SSC | <<locked>> | 82% | 58,218 psi | 87% | 3012 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 59,538 psi | 89% | 2953 fps | 98.4% |
| IMR 8133 Enduron | <<locked>> | 94% | 59,277 psi | 89% | 3038 fps | 100% |
| Lovex D100 | <<locked>> | 90% | 57,928 psi | 87% | 2956 fps | 97.4% |
| Lovex S071 | <<locked>> | 86% | 58,073 psi | 87% | 2887 fps | 100% |
| Norma 217 | <<locked>> | 92% | 57,305 psi | 86% | 3002 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 60,249 psi | 90% | 3038 fps | 100% |
| Ramshot LRT | <<locked>> | 92% | 56,362 psi | 84% | 3035 fps | 96.8% |
| Ramshot Magnum | <<locked>> | 84% | 58,552 psi | 88% | 2959 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,465 psi | 59% | 1969 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 84% | 57,145 psi | 86% | 3025 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 60,278 psi | 90% | 3071 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 57,928 psi | 87% | 2956 fps | 97.4% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 58,682 psi | 88% | 3002 fps | 99.5% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 56,231 psi | 84% | 2982 fps | 98.3% |
| Vihtavuori 24N41 | <<locked>> | 94% | 58,175 psi | 87% | 3009 fps | 96.9% |
| Vihtavuori N165 | <<locked>> | 84% | 60,031 psi | 90% | 2933 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 59,930 psi | 90% | 2995 fps | 99.4% |
| Vihtavuori N565 | <<locked>> | 84% | 57,653 psi | 86% | 2989 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 60,350 psi | 90% | 3074 fps | 100% |
| Vihtavuori N570 | <<locked>> | 88% | 58,189 psi | 87% | 3087 fps | 99.7% |
| Winchester Supreme 780 | <<locked>> | 82% | 59,567 psi | 89% | 2946 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% | 55,724 psi | 84% | 2858 fps | 100% |
| Accurate 8700 | <<locked>> | 88% | 39,900 psi | 60% | 2677 fps | 96.1% |
| ADI AR 2213 | <<locked>> | 80% | 55,463 psi | 83% | 2966 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 42,250 psi | 63% | 2726 fps | 99.7% |
| ADI AR 2218 | 87.9 gr | 80% | 36,448 psi | 55% | 2680 fps | 95.2% |
| ADI AR 2225 | <<locked>> | 80% | 39,668 psi | 59% | 2703 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 56,130 psi | 84% | 2959 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 54,752 psi | 82% | 2858 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 48,936 psi | 73% | 2835 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 80% | 40,988 psi | 61% | 2743 fps | 96.9% |
| Alliant Reloder-50 | <<locked>> | 82% | 38,667 psi | 58% | 2677 fps | 95.4% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 51,779 psi | 78% | 2871 fps | 99.4% |
| Bofors RP15 | <<locked>> | 80% | 52,301 psi | 78% | 2897 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 45,847 psi | 69% | 2802 fps | 99.9% |
| Bofors RP5 | <<locked>> | 80% | 56,130 psi | 84% | 2959 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 46,108 psi | 69% | 2799 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 80% | 56,376 psi | 85% | 2936 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 48,878 psi | 73% | 2923 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,877 psi | 43% | 1722 fps | 100% |
| Hodgdon US 869 | <<locked>> | 92% | 50,082 psi | 75% | 2867 fps | 95% |
| IMR 7828 SSC | <<locked>> | 80% | 54,288 psi | 81% | 2953 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 80% | 46,079 psi | 69% | 2717 fps | 95.5% |
| IMR 8133 Enduron | <<locked>> | 80% | 36,985 psi | 55% | 2631 fps | 98.6% |
| Lovex D100 | <<locked>> | 86% | 50,328 psi | 75% | 2825 fps | 95.6% |
| Lovex S071 | <<locked>> | 80% | 48,167 psi | 72% | 2740 fps | 100% |
| Norma 217 | <<locked>> | 80% | 37,869 psi | 57% | 2654 fps | 99.9% |
| Ramshot Grand | <<locked>> | 80% | 55,898 psi | 84% | 2976 fps | 100% |
| Ramshot LRT | 98.6 gr | 90% | 52,446 psi | 79% | 2966 fps | 95.8% |
| Ramshot Magnum | <<locked>> | 80% | 50,676 psi | 76% | 2844 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,718 psi | 45% | 1765 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 49,124 psi | 74% | 2900 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 44,875 psi | 67% | 2812 fps | 99.4% |
| Shooters World 50 BMG | <<locked>> | 86% | 50,328 psi | 75% | 2825 fps | 95.6% |
| SNPE Vectan SP 13 | <<locked>> | 86% | 39,030 psi | 59% | 2635 fps | 95.3% |
| Vihtavuori 20N29 | <<locked>> | 94% | 45,397 psi | 68% | 2789 fps | 95.8% |
| Vihtavuori 24N41 | <<locked>> | 90% | 50,372 psi | 76% | 2877 fps | 95% |
| Vihtavuori N165 | <<locked>> | 80% | 52,721 psi | 79% | 2828 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 45,803 psi | 69% | 2749 fps | 96.9% |
| Vihtavuori N565 | <<locked>> | 80% | 50,285 psi | 75% | 2867 fps | 100% |
| Vihtavuori N568 | <<locked>> | 80% | 45,455 psi | 68% | 2818 fps | 99.1% |
| Vihtavuori N570 | 86.1 gr | 80% | 43,700 psi | 66% | 2818 fps | 97.3% |
| Winchester Supreme 780 | <<locked>> | 80% | 55,680 psi | 83% | 2887 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 42 powders for 7.21 Firebird loaded with the .284 | 175gr | Speer Grand Slam. ADI AR 2218 delivers the highest muzzle velocity at 3,110 fps; across all powders the maximum-charge window runs from 1,923 fps to 3,110 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 42 of the 42 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 175.0 gr projectile in 0.284" calls for a 1:12.0 twist; slower twists will usually not stabilise this weight. Hodgdon TrailBoss, ReloadSwiss RS 14, Vihtavuori 20N29 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, Ramshot LRT rank at the top here: for 7.21 Firebird with the .284 | 175gr | Speer Grand Slam 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.