Load Specifications
Load data in caliber 7.21 Firebird with .284 | 173gr | Sellier & Bellot SPCE bullet and 43 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.
A valid access license is required to use the Personalized Load Calculator.
You can find more information in our FAQ: How can I use the Personalized Load Calculator?
Max Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 82% | 58,798 psi | 88% | 2913 fps | 100% |
| Accurate 8700 | <<locked>> | 98% | 56,724 psi | 85% | 3002 fps | 99.5% |
| ADI AR 2213 | <<locked>> | 82% | 58,856 psi | 88% | 3035 fps | 100% |
| ADI AR 2217 | <<locked>> | 90% | 59,306 psi | 89% | 3025 fps | 100% |
| ADI AR 2218 | <<locked>> | 92% | 56,376 psi | 85% | 3114 fps | 99.9% |
| ADI AR 2225 | <<locked>> | 92% | 59,712 psi | 90% | 3045 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 59,422 psi | 89% | 3022 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 82% | 57,740 psi | 87% | 2913 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 86% | 59,321 psi | 89% | 3002 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 90% | 58,465 psi | 88% | 3081 fps | 99.8% |
| Alliant Reloder-50 | <<locked>> | 94% | 59,422 psi | 89% | 3091 fps | 99.7% |
| Baschieri & Pellagri 109 | <<locked>> | 84% | 58,349 psi | 87% | 2992 fps | 99.8% |
| Bofors RP15 | <<locked>> | 84% | 59,001 psi | 88% | 3015 fps | 100% |
| Bofors RP30 | <<locked>> | 88% | 59,219 psi | 89% | 3038 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 59,422 psi | 89% | 3022 fps | 100% |
| Hodgdon H1000 | <<locked>> | 86% | 56,391 psi | 85% | 2979 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 59,741 psi | 90% | 2999 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 86% | 59,741 psi | 90% | 3107 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,392 psi | 58% | 1936 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 57,014 psi | 85% | 3002 fps | 96.6% |
| IMR 4955 Enduron | <<locked>> | 82% | 60,191 psi | 90% | 2986 fps | 100% |
| IMR 7828 SSC | <<locked>> | 82% | 57,609 psi | 86% | 3018 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 59,001 psi | 88% | 2956 fps | 98.2% |
| IMR 8133 Enduron | <<locked>> | 94% | 58,581 psi | 88% | 3045 fps | 100% |
| Lovex D100 | <<locked>> | 90% | 57,377 psi | 86% | 2956 fps | 97.1% |
| Lovex S071 | <<locked>> | 86% | 57,508 psi | 86% | 2894 fps | 100% |
| Norma 217 | <<locked>> | 92% | 56,608 psi | 85% | 3005 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 59,553 psi | 89% | 3045 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 59,901 psi | 90% | 3107 fps | 97.4% |
| Ramshot Magnum | <<locked>> | 84% | 57,914 psi | 87% | 2966 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,407 psi | 59% | 1978 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 84% | 56,405 psi | 85% | 3028 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 59,567 psi | 89% | 3074 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 57,377 psi | 86% | 2956 fps | 97.1% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 58,073 psi | 87% | 3005 fps | 99.4% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 55,419 psi | 83% | 2982 fps | 98.1% |
| Vihtavuori 24N41 | <<locked>> | 94% | 57,363 psi | 86% | 3009 fps | 96.6% |
| Vihtavuori N165 | <<locked>> | 84% | 59,480 psi | 89% | 2940 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 59,205 psi | 89% | 2999 fps | 99.2% |
| Vihtavuori N565 | <<locked>> | 84% | 56,855 psi | 85% | 2992 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 59,509 psi | 89% | 3074 fps | 100% |
| Vihtavuori N570 | <<locked>> | 88% | 57,334 psi | 86% | 3091 fps | 99.6% |
| Winchester Supreme 780 | <<locked>> | 82% | 59,016 psi | 88% | 2953 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% | 55,158 psi | 83% | 2861 fps | 100% |
| Accurate 8700 | <<locked>> | 88% | 39,233 psi | 59% | 2674 fps | 95.7% |
| ADI AR 2213 | <<locked>> | 80% | 54,882 psi | 82% | 2969 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 41,727 psi | 63% | 2730 fps | 99.6% |
| ADI AR 2218 | 89.8 gr | 82% | 38,624 psi | 58% | 2746 fps | 96.1% |
| ADI AR 2225 | <<locked>> | 80% | 39,117 psi | 59% | 2703 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 55,550 psi | 83% | 2963 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 54,172 psi | 81% | 2864 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 48,356 psi | 72% | 2838 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 80% | 40,422 psi | 61% | 2740 fps | 96.5% |
| Alliant Reloder-50 | <<locked>> | 82% | 38,159 psi | 57% | 2677 fps | 95.1% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 51,111 psi | 77% | 2874 fps | 99.2% |
| Bofors RP15 | <<locked>> | 80% | 51,750 psi | 78% | 2904 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 45,295 psi | 68% | 2805 fps | 99.9% |
| Bofors RP5 | <<locked>> | 80% | 55,550 psi | 83% | 2963 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 45,542 psi | 68% | 2802 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 80% | 55,840 psi | 84% | 2943 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 48,211 psi | 72% | 2930 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,819 psi | 43% | 1732 fps | 100% |
| Hodgdon US 869 | <<locked>> | 94% | 53,127 psi | 80% | 2936 fps | 95.7% |
| IMR 4955 Enduron | <<locked>> | 80% | 56,434 psi | 85% | 2927 fps | 100% |
| IMR 7828 SSC | <<locked>> | 80% | 53,693 psi | 80% | 2956 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 80% | 45,643 psi | 68% | 2720 fps | 95.2% |
| IMR 8133 Enduron | <<locked>> | 80% | 36,492 psi | 55% | 2628 fps | 98.4% |
| Lovex D100 | <<locked>> | 86% | 49,835 psi | 75% | 2828 fps | 95.3% |
| Lovex S071 | <<locked>> | 80% | 47,645 psi | 71% | 2746 fps | 100% |
| Norma 217 | <<locked>> | 80% | 37,362 psi | 56% | 2657 fps | 99.8% |
| Ramshot Grand | <<locked>> | 80% | 55,230 psi | 83% | 2982 fps | 100% |
| Ramshot LRT | 98.4 gr | 90% | 51,880 psi | 78% | 2969 fps | 95.5% |
| Ramshot Magnum | <<locked>> | 80% | 49,908 psi | 75% | 2844 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,776 psi | 45% | 1775 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 48,269 psi | 72% | 2904 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 44,280 psi | 66% | 2812 fps | 99.2% |
| Shooters World 50 BMG | <<locked>> | 86% | 49,835 psi | 75% | 2828 fps | 95.3% |
| SNPE Vectan SP 13 | <<locked>> | 86% | 38,551 psi | 58% | 2638 fps | 95% |
| Vihtavuori 20N29 | <<locked>> | 94% | 44,817 psi | 67% | 2789 fps | 95.4% |
| Vihtavuori 24N41 | <<locked>> | 92% | 53,548 psi | 80% | 2946 fps | 95.7% |
| Vihtavuori N165 | <<locked>> | 80% | 52,214 psi | 78% | 2835 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 45,339 psi | 68% | 2753 fps | 96.7% |
| Vihtavuori N565 | <<locked>> | 80% | 49,734 psi | 75% | 2874 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 80% | 44,904 psi | 67% | 2822 fps | 99% |
| Vihtavuori N570 | 85.9 gr | 80% | 43,134 psi | 65% | 2818 fps | 97% |
| Winchester Supreme 780 | <<locked>> | 80% | 55,143 psi | 83% | 2894 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 44 powders for 7.21 Firebird loaded with the .284 | 173gr | Sellier & Bellot SPCE. ADI AR 2218 delivers the highest muzzle velocity at 3,114 fps; across all powders the maximum-charge window runs from 1,936 fps to 3,114 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 44 of the 44 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 173.0 gr projectile in 0.284" calls for a 1:11.5 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, Vihtavuori N570, Ramshot LRT rank at the top here: for 7.21 Firebird with the .284 | 173gr | Sellier & Bellot SPCE 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.