Load Specifications
Load data in caliber 7.21 Firebird with .284 | 170gr | Sierra RN Prohunter bullet and 44 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% | 58,726 psi | 88% | 2936 fps | 100% |
| Accurate 8700 | <<locked>> | 98% | 56,507 psi | 85% | 3018 fps | 99.4% |
| ADI AR 2213 | <<locked>> | 82% | 58,552 psi | 88% | 3051 fps | 100% |
| ADI AR 2217 | <<locked>> | 90% | 59,074 psi | 89% | 3045 fps | 100% |
| ADI AR 2218 | <<locked>> | 92% | 56,202 psi | 84% | 3130 fps | 99.8% |
| ADI AR 2225 | <<locked>> | 92% | 59,611 psi | 89% | 3068 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 59,132 psi | 89% | 3041 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 82% | 57,522 psi | 86% | 2936 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 86% | 58,972 psi | 88% | 3022 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 90% | 58,305 psi | 87% | 3100 fps | 99.8% |
| Alliant Reloder-50 | <<locked>> | 94% | 59,146 psi | 89% | 3104 fps | 99.6% |
| Baschieri & Pellagri 109 | <<locked>> | 84% | 58,175 psi | 87% | 3012 fps | 99.8% |
| Bofors RP15 | <<locked>> | 84% | 58,711 psi | 88% | 3035 fps | 100% |
| Bofors RP30 | <<locked>> | 88% | 59,030 psi | 88% | 3058 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 59,132 psi | 89% | 3041 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 60,350 psi | 90% | 3058 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 59,480 psi | 89% | 3018 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 86% | 59,553 psi | 89% | 3127 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,363 psi | 57% | 1952 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 56,782 psi | 85% | 3018 fps | 96.4% |
| IMR 4955 Enduron | <<locked>> | 82% | 59,959 psi | 90% | 3005 fps | 100% |
| IMR 7828 SSC | <<locked>> | 82% | 57,522 psi | 86% | 3038 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 58,856 psi | 88% | 2976 fps | 98.1% |
| IMR 8133 Enduron | <<locked>> | 94% | 58,334 psi | 87% | 3061 fps | 100% |
| Lovex D100 | <<locked>> | 90% | 57,217 psi | 86% | 2976 fps | 97% |
| Lovex S071 | <<locked>> | 86% | 57,421 psi | 86% | 2917 fps | 100% |
| Norma 217 | <<locked>> | 92% | 56,347 psi | 84% | 3025 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 59,205 psi | 89% | 3064 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 59,683 psi | 89% | 3127 fps | 97.2% |
| Ramshot Magnum | <<locked>> | 84% | 57,711 psi | 87% | 2986 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,378 psi | 59% | 1995 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 84% | 56,159 psi | 84% | 3048 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 59,451 psi | 89% | 3097 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 57,217 psi | 86% | 2976 fps | 97% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 57,870 psi | 87% | 3022 fps | 99.3% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 55,332 psi | 83% | 3002 fps | 98% |
| Vihtavuori 24N41 | <<locked>> | 94% | 57,188 psi | 86% | 3025 fps | 96.4% |
| Vihtavuori N165 | <<locked>> | 84% | 59,350 psi | 89% | 2963 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 59,132 psi | 89% | 3015 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 84% | 56,695 psi | 85% | 3012 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 59,451 psi | 89% | 3097 fps | 100% |
| Vihtavuori N570 | <<locked>> | 88% | 57,246 psi | 86% | 3110 fps | 99.5% |
| Winchester StaBALL HD | <<locked>> | 82% | 60,205 psi | 90% | 3038 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 58,740 psi | 88% | 2969 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% | 54,926 psi | 82% | 2881 fps | 100% |
| Accurate 8700 | <<locked>> | 88% | 39,160 psi | 59% | 2690 fps | 95.5% |
| ADI AR 2213 | <<locked>> | 80% | 54,636 psi | 82% | 2989 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 41,524 psi | 62% | 2746 fps | 99.5% |
| ADI AR 2218 | 90.6 gr | 82% | 38,479 psi | 58% | 2762 fps | 95.8% |
| ADI AR 2225 | <<locked>> | 80% | 39,030 psi | 59% | 2723 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 55,317 psi | 83% | 2982 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 53,954 psi | 81% | 2884 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 48,298 psi | 72% | 2861 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 80% | 40,147 psi | 60% | 2753 fps | 96.3% |
| Alliant Reloder-50 | <<locked>> | 84% | 40,988 psi | 61% | 2762 fps | 96% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 51,039 psi | 77% | 2894 fps | 99.1% |
| Bofors RP15 | <<locked>> | 80% | 51,561 psi | 77% | 2923 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 45,092 psi | 68% | 2822 fps | 99.8% |
| Bofors RP5 | <<locked>> | 80% | 55,317 psi | 83% | 2982 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 45,295 psi | 68% | 2818 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 80% | 55,608 psi | 83% | 2963 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 48,109 psi | 72% | 2946 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,877 psi | 43% | 1749 fps | 100% |
| Hodgdon US 869 | <<locked>> | 94% | 52,924 psi | 79% | 2949 fps | 95.5% |
| IMR 4955 Enduron | <<locked>> | 80% | 56,391 psi | 85% | 2949 fps | 100% |
| IMR 7828 SSC | <<locked>> | 80% | 53,635 psi | 80% | 2979 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 80% | 45,469 psi | 68% | 2736 fps | 95% |
| IMR 8133 Enduron | <<locked>> | 80% | 36,303 psi | 54% | 2644 fps | 98.2% |
| Lovex D100 | <<locked>> | 86% | 49,632 psi | 74% | 2844 fps | 95.1% |
| Lovex S071 | <<locked>> | 80% | 47,500 psi | 71% | 2766 fps | 100% |
| Norma 217 | <<locked>> | 80% | 37,144 psi | 56% | 2671 fps | 99.7% |
| Ramshot Grand | <<locked>> | 80% | 55,100 psi | 83% | 3002 fps | 100% |
| Ramshot LRT | 99.3 gr | 90% | 51,721 psi | 78% | 2986 fps | 95.3% |
| Ramshot Magnum | <<locked>> | 80% | 49,777 psi | 75% | 2864 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,689 psi | 45% | 1791 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 48,109 psi | 72% | 2920 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 43,976 psi | 66% | 2825 fps | 99% |
| Shooters World 50 BMG | <<locked>> | 86% | 49,632 psi | 74% | 2844 fps | 95.1% |
| SNPE Vectan SP 13 | <<locked>> | 88% | 41,118 psi | 62% | 2713 fps | 95.8% |
| Vihtavuori 20N29 | <<locked>> | 94% | 44,672 psi | 67% | 2802 fps | 95.2% |
| Vihtavuori 24N41 | <<locked>> | 92% | 53,243 psi | 80% | 2959 fps | 95.5% |
| Vihtavuori N165 | <<locked>> | 80% | 52,011 psi | 78% | 2854 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 45,107 psi | 68% | 2769 fps | 96.5% |
| Vihtavuori N565 | <<locked>> | 80% | 49,632 psi | 74% | 2890 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 80% | 44,773 psi | 67% | 2838 fps | 98.8% |
| Vihtavuori N570 | 86.6 gr | 80% | 42,873 psi | 64% | 2831 fps | 96.7% |
| Winchester StaBALL HD | <<locked>> | 80% | 55,854 psi | 84% | 2979 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 54,911 psi | 82% | 2913 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 | 170gr | Sierra RN Prohunter. ADI AR 2218 delivers the highest muzzle velocity at 3,130 fps; across all powders the maximum-charge window runs from 1,952 fps to 3,130 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 57–90 %, leaving at least 10 % headroom. The 170.0 gr projectile in 0.284" calls for a 1:12.5 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 | 170gr | Sierra RN Prohunter 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.