Load Specifications
Load data in caliber 7.21 Firebird with .284 | 175gr | Barnes X S bullet and 35 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 Alliant Reloder-33.
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 8700 | <<locked>> | 98% | 59,146 psi | 89% | 3018 fps | 99.7% |
| ADI AR 2217 | <<locked>> | 88% | 57,435 psi | 86% | 2976 fps | 100% |
| ADI AR 2218 | <<locked>> | 92% | 58,711 psi | 88% | 3133 fps | 100% |
| ADI AR 2225 | <<locked>> | 90% | 58,334 psi | 87% | 3009 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 82% | 60,278 psi | 90% | 2920 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 84% | 57,856 psi | 87% | 2959 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 88% | 57,087 psi | 86% | 3041 fps | 99.8% |
| Alliant Reloder-50 | <<locked>> | 92% | 58,711 psi | 88% | 3058 fps | 99.7% |
| Baschieri & Pellagri 109 | <<locked>> | 84% | 59,785 psi | 90% | 2992 fps | 99.9% |
| Bofors RP15 | <<locked>> | 82% | 57,624 psi | 86% | 2969 fps | 100% |
| Bofors RP30 | <<locked>> | 86% | 58,175 psi | 87% | 2999 fps | 100% |
| Hodgdon H1000 | <<locked>> | 86% | 58,610 psi | 88% | 2986 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 84% | 58,117 psi | 87% | 3064 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,522 psi | 58% | 1916 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 59,292 psi | 89% | 3015 fps | 97.1% |
| IMR 7828 SSC | <<locked>> | 82% | 59,741 psi | 90% | 3025 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 86% | 57,130 psi | 86% | 2900 fps | 97.9% |
| IMR 8133 Enduron | <<locked>> | 92% | 57,653 psi | 86% | 3005 fps | 100% |
| Lovex D100 | <<locked>> | 90% | 59,625 psi | 89% | 2969 fps | 97.5% |
| Lovex S071 | <<locked>> | 84% | 57,159 psi | 86% | 2861 fps | 100% |
| Norma 217 | <<locked>> | 92% | 59,698 psi | 89% | 3025 fps | 100% |
| Ramshot LRT | <<locked>> | 92% | 57,928 psi | 87% | 3054 fps | 97% |
| Ramshot Magnum | <<locked>> | 82% | 56,434 psi | 85% | 2920 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,769 psi | 60% | 1962 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 84% | 59,132 psi | 89% | 3048 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 86% | 58,363 psi | 87% | 3038 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 59,625 psi | 89% | 2969 fps | 97.5% |
| SNPE Vectan SP 13 | <<locked>> | 96% | 57,029 psi | 85% | 2966 fps | 99.3% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 58,334 psi | 87% | 3009 fps | 98.6% |
| Vihtavuori 24N41 | <<locked>> | 94% | 59,611 psi | 89% | 3022 fps | 97.1% |
| Vihtavuori N165 | <<locked>> | 82% | 58,015 psi | 87% | 2894 fps | 100% |
| Vihtavuori N170 | <<locked>> | 86% | 57,914 psi | 87% | 2953 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 84% | 59,683 psi | 89% | 3009 fps | 100% |
| Vihtavuori N568 | <<locked>> | 86% | 58,305 psi | 87% | 3035 fps | 100% |
| Vihtavuori N570 | <<locked>> | 88% | 60,075 psi | 90% | 3110 fps | 99.8% |
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 8700 | <<locked>> | 86% | 39,262 psi | 59% | 2657 fps | 95.9% |
| ADI AR 2217 | <<locked>> | 80% | 44,092 psi | 66% | 2756 fps | 99.9% |
| ADI AR 2218 | 85.3 gr | 80% | 38,522 psi | 58% | 2726 fps | 96.2% |
| ADI AR 2225 | <<locked>> | 80% | 41,814 psi | 63% | 2740 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 56,608 psi | 85% | 2874 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 50,865 psi | 76% | 2858 fps | 100% |
| Alliant Reloder-33 | 86.8 gr | 80% | 43,221 psi | 65% | 2785 fps | 97.6% |
| Alliant Reloder-50 | <<locked>> | 80% | 39,088 psi | 59% | 2684 fps | 95.7% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 52,794 psi | 79% | 2881 fps | 99.4% |
| Bofors RP15 | <<locked>> | 80% | 54,157 psi | 81% | 2917 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 48,124 psi | 72% | 2835 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 47,761 psi | 72% | 2818 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 50,836 psi | 76% | 2953 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 29,138 psi | 44% | 1716 fps | 100% |
| Hodgdon US 869 | <<locked>> | 92% | 52,069 psi | 78% | 2894 fps | 95.4% |
| IMR 7828 SSC | <<locked>> | 80% | 55,970 psi | 84% | 2969 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 80% | 47,543 psi | 71% | 2733 fps | 95.8% |
| IMR 8133 Enduron | <<locked>> | 80% | 39,465 psi | 59% | 2680 fps | 99.2% |
| Lovex D100 | <<locked>> | 84% | 48,892 psi | 73% | 2789 fps | 95.1% |
| Lovex S071 | <<locked>> | 80% | 50,763 psi | 76% | 2766 fps | 100% |
| Norma 217 | <<locked>> | 80% | 40,538 psi | 61% | 2707 fps | 100% |
| Ramshot LRT | 93.6 gr | 88% | 50,531 psi | 76% | 2923 fps | 95.2% |
| Ramshot Magnum | <<locked>> | 80% | 52,707 psi | 79% | 2867 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 30,037 psi | 45% | 1755 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 51,198 psi | 77% | 2930 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 47,224 psi | 71% | 2851 fps | 99.6% |
| Shooters World 50 BMG | <<locked>> | 84% | 48,892 psi | 73% | 2789 fps | 95.1% |
| SNPE Vectan SP 13 | <<locked>> | 84% | 38,899 psi | 58% | 2625 fps | 95.3% |
| Vihtavuori 20N29 | <<locked>> | 92% | 44,831 psi | 67% | 2769 fps | 95.5% |
| Vihtavuori 24N41 | <<locked>> | 90% | 52,170 psi | 78% | 2897 fps | 95.4% |
| Vihtavuori N165 | <<locked>> | 80% | 54,520 psi | 82% | 2844 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 47,863 psi | 72% | 2779 fps | 97.4% |
| Vihtavuori N565 | <<locked>> | 80% | 52,562 psi | 79% | 2897 fps | 100% |
| Vihtavuori N568 | <<locked>> | 80% | 47,747 psi | 72% | 2854 fps | 99.4% |
| Vihtavuori N570 | <<locked>> | 80% | 45,861 psi | 69% | 2858 fps | 97.9% |
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 35 powders for 7.21 Firebird loaded with the .284 | 175gr | Barnes X S. ADI AR 2218 delivers the highest muzzle velocity at 3,133 fps; across all powders the maximum-charge window runs from 1,916 fps to 3,133 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 35 of the 35 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (460 MPa), the top charges use 58–90 %, leaving at least 10 % headroom. The 175.0 gr projectile in 0.284" calls for a 1:9.5 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, Ramshot LRT, Alliant Reloder-33 rank at the top here: for 7.21 Firebird with the .284 | 175gr | Barnes X S 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.