Load Specifications
Load data in caliber 7.21 Firebird with .284 | 153gr | Peregrine Glider GRM bullet and 52 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2218, Hodgdon Retumbo and Vihtavuori N570.
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>> | 86% | 58,334 psi | 87% | 3068 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 50,473 psi | 76% | 3045 fps | 97.5% |
| Accurate MAGPRO | <<locked>> | 84% | 57,914 psi | 87% | 3196 fps | 99.9% |
| ADI AR 2209 | <<locked>> | 84% | 59,495 psi | 89% | 3166 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 58,494 psi | 88% | 3189 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 58,001 psi | 87% | 3169 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 59,088 psi | 89% | 3314 fps | 99.6% |
| ADI AR 2225 | <<locked>> | 96% | 57,769 psi | 87% | 3192 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 59,059 psi | 89% | 3156 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 58,842 psi | 88% | 3179 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 56,985 psi | 85% | 3074 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 58,073 psi | 87% | 3159 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 57,914 psi | 87% | 3166 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 56,710 psi | 85% | 3212 fps | 99% |
| Alliant Reloder-50 | <<locked>> | 98% | 56,681 psi | 85% | 3199 fps | 98.7% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 58,653 psi | 88% | 3146 fps | 99.3% |
| Bofors RP15 | <<locked>> | 88% | 58,218 psi | 87% | 3169 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 57,870 psi | 87% | 3182 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 58,842 psi | 88% | 3179 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 59,466 psi | 89% | 3189 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 56,927 psi | 85% | 3114 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 86% | 59,901 psi | 90% | 3163 fps | 100% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 59,451 psi | 89% | 3054 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 57,914 psi | 87% | 3261 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,826 psi | 57% | 2028 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 56,971 psi | 85% | 3091 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 86% | 57,116 psi | 86% | 3176 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 92% | 59,640 psi | 89% | 3104 fps | 97% |
| IMR 8133 Enduron | <<locked>> | 98% | 56,347 psi | 84% | 3173 fps | 100% |
| Lovex S071 | <<locked>> | 92% | 60,365 psi | 90% | 3100 fps | 100% |
| Norma 217 | <<locked>> | 98% | 57,798 psi | 87% | 3192 fps | 100% |
| Norma MRP | <<locked>> | 84% | 59,132 psi | 89% | 3192 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 58,769 psi | 88% | 3199 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 57,000 psi | 85% | 3117 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,914 psi | 58% | 2077 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 58,943 psi | 88% | 3241 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 57,769 psi | 87% | 3212 fps | 99.9% |
| Rottweil R 904 | <<locked>> | 84% | 59,654 psi | 89% | 3136 fps | 100% |
| Rottweil R 905 | <<locked>> | 84% | 58,972 psi | 88% | 3150 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 52,359 psi | 78% | 3058 fps | 97.6% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 58,610 psi | 88% | 3146 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 57,246 psi | 86% | 3064 fps | 99.9% |
| Somchem S385 | <<locked>> | 84% | 59,045 psi | 89% | 3110 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 59,364 psi | 89% | 3100 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 58,711 psi | 88% | 3136 fps | 98.2% |
| Vihtavuori N555 | <<locked>> | 84% | 58,624 psi | 88% | 3104 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 58,436 psi | 88% | 3202 fps | 100% |
| Vihtavuori N565 | <<locked>> | 90% | 59,799 psi | 90% | 3196 fps | 100% |
| Vihtavuori N568 | <<locked>> | 92% | 58,044 psi | 87% | 3215 fps | 99.8% |
| Vihtavuori N570 | <<locked>> | 94% | 59,770 psi | 90% | 3291 fps | 99.2% |
| Winchester StaBALL HD | <<locked>> | 86% | 58,407 psi | 88% | 3173 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 59,088 psi | 89% | 3110 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% | 47,456 psi | 71% | 2897 fps | 100% |
| Accurate 8700 | <<locked>> | 96% | 43,381 psi | 65% | 2907 fps | 95.5% |
| Accurate MAGPRO | <<locked>> | 80% | 49,995 psi | 75% | 3058 fps | 99.1% |
| ADI AR 2209 | <<locked>> | 80% | 52,040 psi | 78% | 3048 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 47,297 psi | 71% | 2995 fps | 99.4% |
| ADI AR 2217 | <<locked>> | 80% | 34,998 psi | 52% | 2717 fps | 96.8% |
| ADI AR 2218 | 95.4 gr | 90% | 43,439 psi | 65% | 3002 fps | 96.2% |
| ADI AR 2225 | <<locked>> | 80% | 32,271 psi | 48% | 2680 fps | 98.6% |
| Alliant Reloder-19 | <<locked>> | 80% | 51,692 psi | 77% | 3038 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 47,935 psi | 72% | 2995 fps | 99.9% |
| Alliant Reloder-23 | <<locked>> | 80% | 46,601 psi | 70% | 2913 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 40,814 psi | 61% | 2864 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 53,780 psi | 81% | 3104 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 86% | 41,553 psi | 62% | 2913 fps | 95.4% |
| Alliant Reloder-50 | <<locked>> | 92% | 44,933 psi | 67% | 2976 fps | 96% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 44,933 psi | 67% | 2897 fps | 96.8% |
| Bofors RP15 | <<locked>> | 80% | 44,454 psi | 67% | 2923 fps | 99.5% |
| Bofors RP30 | <<locked>> | 80% | 37,913 psi | 57% | 2795 fps | 97.7% |
| Bofors RP5 | <<locked>> | 80% | 47,935 psi | 72% | 2995 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 80% | 38,305 psi | 57% | 2802 fps | 98.4% |
| Hodgdon H4831 | <<locked>> | 80% | 49,617 psi | 74% | 2989 fps | 99.3% |
| Hodgdon H4831 SC | <<locked>> | 80% | 48,747 psi | 73% | 2972 fps | 99.2% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 55,738 psi | 84% | 3002 fps | 100% |
| Hodgdon Retumbo | 80 gr | 80% | 39,813 psi | 60% | 2923 fps | 99.5% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,384 psi | 43% | 1818 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 50,125 psi | 75% | 2972 fps | 99.4% |
| IMR 7828 SSC | <<locked>> | 80% | 46,093 psi | 69% | 2979 fps | 99.2% |
| IMR 7977 Enduron | <<locked>> | 88% | 52,185 psi | 78% | 2979 fps | 95.3% |
| IMR 8133 Enduron | <<locked>> | 82% | 31,995 psi | 48% | 2657 fps | 95.2% |
| Lovex S071 | <<locked>> | 80% | 40,770 psi | 61% | 2769 fps | 100% |
| Norma 217 | <<locked>> | 80% | 30,124 psi | 45% | 2618 fps | 96.7% |
| Norma MRP | <<locked>> | 80% | 51,343 psi | 77% | 3068 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 46,746 psi | 70% | 2995 fps | 99.5% |
| Ramshot Magnum | <<locked>> | 80% | 41,930 psi | 63% | 2854 fps | 99.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,138 psi | 44% | 1860 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 39,566 psi | 59% | 2897 fps | 99.9% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 36,260 psi | 54% | 2776 fps | 95.6% |
| Rottweil R 904 | <<locked>> | 80% | 52,388 psi | 79% | 3015 fps | 99.8% |
| Rottweil R 905 | <<locked>> | 80% | 51,430 psi | 77% | 3028 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 96% | 45,353 psi | 68% | 2923 fps | 95.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 51,097 psi | 77% | 3025 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 53,519 psi | 80% | 3005 fps | 99.7% |
| Somchem S385 | <<locked>> | 80% | 51,706 psi | 78% | 2995 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 45,310 psi | 68% | 2867 fps | 99.8% |
| Vihtavuori N170 | <<locked>> | 86% | 47,776 psi | 72% | 2940 fps | 95.8% |
| Vihtavuori N555 | <<locked>> | 80% | 51,358 psi | 77% | 2995 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 50,807 psi | 76% | 3071 fps | 99.5% |
| Vihtavuori N565 | <<locked>> | 80% | 42,221 psi | 63% | 2877 fps | 98.2% |
| Vihtavuori N568 | <<locked>> | 80% | 37,275 psi | 56% | 2795 fps | 95.4% |
| Vihtavuori N570 | 89.3 gr | 86% | 44,469 psi | 67% | 2999 fps | 95.9% |
| Winchester StaBALL HD | <<locked>> | 80% | 46,325 psi | 69% | 2989 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 47,863 psi | 72% | 2927 fps | 99.9% |
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 59 powders for 7.21 Firebird loaded with the .284 | 153gr | Peregrine Glider GRM. ADI AR 2218 delivers the highest muzzle velocity at 3,314 fps; across all powders the maximum-charge window runs from 2,028 fps to 3,314 fps. Accurate 8700 gives the best case fill at 100 %, and 59 of the 59 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 153.0 gr projectile in 0.284" calls for a 1:8.0 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, Hodgdon US 869 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, Hodgdon Retumbo, Vihtavuori N570 rank at the top here: for 7.21 Firebird with the .284 | 153gr | Peregrine Glider GRM they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG, Hodgdon US 869, Vihtavuori 20N29 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.