Load Specifications
Load data in caliber 7.21 Firebird with .284 | 160gr | Sierra SBT GameKing bullet and 48 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 Alliant Reloder-50.
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% | 60,176 psi | 90% | 3031 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 57,537 psi | 86% | 3107 fps | 99.2% |
| Accurate MAGPRO | <<locked>> | 82% | 59,683 psi | 89% | 3163 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 60,147 psi | 90% | 3153 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 60,350 psi | 90% | 3143 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 57,435 psi | 86% | 3228 fps | 99.7% |
| ADI AR 2225 | <<locked>> | 92% | 56,449 psi | 85% | 3104 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 56,782 psi | 85% | 3084 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 58,856 psi | 88% | 3035 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 60,350 psi | 90% | 3123 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 59,538 psi | 89% | 3196 fps | 99.7% |
| Alliant Reloder-50 | <<locked>> | 96% | 60,234 psi | 90% | 3196 fps | 99.5% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 59,698 psi | 89% | 3110 fps | 99.7% |
| Bofors RP15 | <<locked>> | 86% | 60,046 psi | 90% | 3133 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 60,162 psi | 90% | 3153 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 56,782 psi | 85% | 3084 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 57,566 psi | 86% | 3097 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 58,160 psi | 87% | 3077 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 57,232 psi | 86% | 3061 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 86% | 56,521 psi | 85% | 3169 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,116 psi | 57% | 2005 fps | 100% |
| Hodgdon US 869 | <<locked>> | 98% | 58,088 psi | 87% | 3107 fps | 96.1% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,943 psi | 87% | 3048 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 58,813 psi | 88% | 3140 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 56,840 psi | 85% | 3012 fps | 97.1% |
| IMR 8133 Enduron | <<locked>> | 96% | 59,306 psi | 89% | 3156 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 58,827 psi | 88% | 3068 fps | 96.7% |
| Lovex S071 | <<locked>> | 88% | 58,668 psi | 88% | 3012 fps | 100% |
| Norma 217 | <<locked>> | 94% | 57,203 psi | 86% | 3117 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 56,434 psi | 85% | 3100 fps | 100% |
| Ramshot Magnum | <<locked>> | 86% | 59,103 psi | 89% | 3081 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,247 psi | 59% | 2051 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 57,348 psi | 86% | 3150 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 56,304 psi | 84% | 3123 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 60,336 psi | 90% | 3107 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 58,827 psi | 88% | 3068 fps | 96.7% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 59,016 psi | 88% | 3110 fps | 99.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,973 psi | 90% | 3104 fps | 100% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 52,315 psi | 78% | 3018 fps | 96.7% |
| Vihtavuori 24N41 | <<locked>> | 96% | 58,653 psi | 88% | 3120 fps | 96.1% |
| Vihtavuori N165 | <<locked>> | 84% | 56,942 psi | 85% | 3005 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 56,623 psi | 85% | 3048 fps | 98.4% |
| Vihtavuori N560 | <<locked>> | 82% | 60,104 psi | 90% | 3169 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 58,001 psi | 87% | 3107 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 56,449 psi | 85% | 3127 fps | 99.9% |
| Vihtavuori N570 | <<locked>> | 90% | 58,291 psi | 87% | 3202 fps | 99.3% |
| Winchester StaBALL HD | <<locked>> | 82% | 56,927 psi | 85% | 3077 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 56,507 psi | 85% | 3015 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% | 52,779 psi | 79% | 2927 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 42,844 psi | 64% | 2838 fps | 96.1% |
| Accurate MAGPRO | <<locked>> | 80% | 55,651 psi | 83% | 3097 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 52,344 psi | 78% | 3028 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 39,494 psi | 59% | 2772 fps | 98.8% |
| ADI AR 2218 | 92.8 gr | 84% | 39,349 psi | 59% | 2844 fps | 95.3% |
| ADI AR 2225 | <<locked>> | 80% | 36,811 psi | 55% | 2743 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 53,055 psi | 80% | 3025 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 51,721 psi | 78% | 2930 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 45,890 psi | 69% | 2897 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 41,046 psi | 62% | 2841 fps | 95.9% |
| Alliant Reloder-50 | 96.5 gr | 86% | 41,597 psi | 62% | 2841 fps | 95.5% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 49,153 psi | 74% | 2930 fps | 98.4% |
| Bofors RP15 | <<locked>> | 80% | 49,429 psi | 74% | 2963 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 42,946 psi | 64% | 2851 fps | 99.3% |
| Bofors RP5 | <<locked>> | 80% | 53,055 psi | 80% | 3025 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 43,105 psi | 65% | 2848 fps | 99.7% |
| Hodgdon H4831 | <<locked>> | 80% | 54,375 psi | 82% | 3015 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 53,490 psi | 80% | 3002 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 80% | 45,353 psi | 68% | 2976 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,776 psi | 43% | 1798 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 54,143 psi | 81% | 3038 fps | 95.1% |
| IMR 4955 Enduron | <<locked>> | 80% | 54,346 psi | 81% | 2992 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 51,126 psi | 77% | 3012 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 84% | 49,937 psi | 75% | 2890 fps | 95.6% |
| IMR 8133 Enduron | <<locked>> | 80% | 34,374 psi | 52% | 2664 fps | 97% |
| Lovex D100 | <<locked>> | 90% | 54,810 psi | 82% | 3002 fps | 95.8% |
| Lovex S071 | <<locked>> | 80% | 45,571 psi | 68% | 2805 fps | 100% |
| Norma 217 | <<locked>> | 80% | 35,056 psi | 53% | 2690 fps | 99% |
| Ramshot Grand | <<locked>> | 80% | 52,504 psi | 79% | 3038 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 47,427 psi | 71% | 2900 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,573 psi | 44% | 1841 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 45,455 psi | 68% | 2953 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 41,655 psi | 62% | 2848 fps | 98.1% |
| Rottweil R 905 | <<locked>> | 80% | 56,405 psi | 85% | 3048 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 54,810 psi | 82% | 3002 fps | 95.8% |
| SNPE Vectan SP 13 | <<locked>> | 90% | 41,814 psi | 63% | 2792 fps | 95.3% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 56,057 psi | 84% | 3045 fps | 100% |
| Vihtavuori 20N29 | <<locked>> | 98% | 48,762 psi | 73% | 2949 fps | 95.8% |
| Vihtavuori 24N41 | <<locked>> | 94% | 54,578 psi | 82% | 3048 fps | 95.1% |
| Vihtavuori N165 | <<locked>> | 80% | 49,995 psi | 75% | 2894 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 43,236 psi | 65% | 2795 fps | 95.2% |
| Vihtavuori N560 | <<locked>> | 80% | 56,188 psi | 84% | 3107 fps | 100% |
| Vihtavuori N565 | <<locked>> | 80% | 47,282 psi | 71% | 2920 fps | 99.5% |
| Vihtavuori N568 | <<locked>> | 80% | 42,409 psi | 64% | 2858 fps | 97.8% |
| Vihtavuori N570 | 86.6 gr | 80% | 40,625 psi | 61% | 2851 fps | 95.2% |
| Winchester StaBALL HD | <<locked>> | 80% | 52,982 psi | 79% | 3022 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 52,779 psi | 79% | 2956 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 48 powders for 7.21 Firebird loaded with the .284 | 160gr | Sierra SBT GameKing. ADI AR 2218 delivers the highest muzzle velocity at 3,228 fps; across all powders the maximum-charge window runs from 2,005 fps to 3,228 fps. Accurate 8700 gives the best case fill at 100 %, and 48 of the 48 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 160.0 gr projectile in 0.284" calls for a 1:11.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, ReloadSwiss RS 14 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, Alliant Reloder-50 rank at the top here: for 7.21 Firebird with the .284 | 160gr | Sierra SBT GameKing 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.