Load Specifications
Load data in caliber 7.21 Firebird with .284 | 150gr | Sierra GameKing bullet and 50 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>> | 84% | 58,204 psi | 87% | 3091 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 55,056 psi | 83% | 3140 fps | 98.5% |
| Accurate MAGPRO | <<locked>> | 82% | 57,493 psi | 86% | 3209 fps | 99.8% |
| ADI AR 2209 | <<locked>> | 82% | 58,914 psi | 88% | 3182 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 58,073 psi | 87% | 3205 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 58,059 psi | 87% | 3192 fps | 100% |
| ADI AR 2218 | <<locked>> | 96% | 59,132 psi | 89% | 3333 fps | 99.6% |
| ADI AR 2225 | <<locked>> | 94% | 58,001 psi | 87% | 3212 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 58,363 psi | 87% | 3169 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 58,595 psi | 88% | 3196 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 56,840 psi | 85% | 3091 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 58,030 psi | 87% | 3176 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 57,130 psi | 86% | 3232 fps | 99.1% |
| Alliant Reloder-50 | <<locked>> | 96% | 57,624 psi | 86% | 3228 fps | 98.9% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 57,957 psi | 87% | 3159 fps | 99.3% |
| Bofors RP15 | <<locked>> | 86% | 58,001 psi | 87% | 3186 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 57,972 psi | 87% | 3205 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 58,595 psi | 88% | 3196 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 59,321 psi | 89% | 3205 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 56,304 psi | 84% | 3127 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 84% | 59,234 psi | 89% | 3173 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 58,030 psi | 87% | 3278 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,130 psi | 57% | 2067 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 60,046 psi | 90% | 3163 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 56,681 psi | 85% | 3189 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 58,827 psi | 88% | 3117 fps | 96.9% |
| IMR 8133 Enduron | <<locked>> | 96% | 56,927 psi | 85% | 3199 fps | 100% |
| Lovex S071 | <<locked>> | 88% | 56,739 psi | 85% | 3068 fps | 100% |
| Norma 217 | <<locked>> | 96% | 58,726 psi | 88% | 3222 fps | 100% |
| Norma MRP | <<locked>> | 82% | 59,001 psi | 88% | 3209 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 58,421 psi | 88% | 3215 fps | 100% |
| Ramshot Magnum | <<locked>> | 86% | 56,913 psi | 85% | 3133 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,204 psi | 59% | 2113 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 88% | 59,132 psi | 89% | 3258 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 58,204 psi | 87% | 3235 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 58,842 psi | 88% | 3146 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 58,450 psi | 88% | 3163 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 56,753 psi | 85% | 3146 fps | 98.4% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 58,088 psi | 87% | 3159 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 60,365 psi | 90% | 3133 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 58,653 psi | 88% | 3127 fps | 100% |
| Vihtavuori N165 | <<locked>> | 86% | 58,856 psi | 88% | 3114 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 58,595 psi | 88% | 3153 fps | 98.2% |
| Vihtavuori N555 | <<locked>> | 82% | 58,552 psi | 88% | 3123 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 58,146 psi | 87% | 3219 fps | 100% |
| Vihtavuori N565 | <<locked>> | 88% | 59,828 psi | 90% | 3215 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 58,276 psi | 87% | 3235 fps | 99.8% |
| Vihtavuori N570 | <<locked>> | 92% | 60,133 psi | 90% | 3310 fps | 99.2% |
| Winchester StaBALL HD | <<locked>> | 84% | 58,726 psi | 88% | 3189 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 58,465 psi | 88% | 3123 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% | 50,879 psi | 76% | 2976 fps | 100% |
| Accurate 8700 | <<locked>> | 94% | 44,063 psi | 66% | 2930 fps | 95.8% |
| Accurate MAGPRO | <<locked>> | 80% | 53,606 psi | 80% | 3143 fps | 99.5% |
| ADI AR 2209 | <<locked>> | 80% | 55,085 psi | 83% | 3120 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 50,517 psi | 76% | 3074 fps | 99.7% |
| ADI AR 2217 | <<locked>> | 80% | 37,797 psi | 57% | 2802 fps | 97.8% |
| ADI AR 2218 | 95.9 gr | 86% | 40,611 psi | 61% | 2943 fps | 95% |
| ADI AR 2225 | <<locked>> | 80% | 35,215 psi | 53% | 2776 fps | 99.4% |
| Alliant Reloder-19 | <<locked>> | 80% | 54,665 psi | 82% | 3110 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 51,256 psi | 77% | 3074 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 49,821 psi | 75% | 2986 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 44,092 psi | 66% | 2943 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 84% | 42,250 psi | 63% | 2940 fps | 95.6% |
| Alliant Reloder-50 | <<locked>> | 88% | 42,656 psi | 64% | 2936 fps | 95.1% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 47,616 psi | 71% | 2969 fps | 97.6% |
| Bofors RP15 | <<locked>> | 80% | 47,587 psi | 71% | 3005 fps | 99.8% |
| Bofors RP30 | <<locked>> | 80% | 41,118 psi | 62% | 2884 fps | 98.6% |
| Bofors RP5 | <<locked>> | 80% | 51,256 psi | 77% | 3074 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 41,336 psi | 62% | 2887 fps | 99.1% |
| Hodgdon H4831 | <<locked>> | 80% | 52,620 psi | 79% | 3064 fps | 99.6% |
| Hodgdon H4831 SC | <<locked>> | 80% | 51,779 psi | 78% | 3048 fps | 99.6% |
| Hodgdon Retumbo | 84.2 gr | 80% | 43,308 psi | 65% | 3015 fps | 99.9% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,601 psi | 43% | 1850 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 52,808 psi | 79% | 3045 fps | 99.7% |
| IMR 7828 SSC | <<locked>> | 80% | 49,284 psi | 74% | 3058 fps | 99.6% |
| IMR 7977 Enduron | <<locked>> | 86% | 51,590 psi | 77% | 2992 fps | 95.3% |
| IMR 8133 Enduron | <<locked>> | 80% | 32,750 psi | 49% | 2684 fps | 95.5% |
| Lovex S071 | <<locked>> | 80% | 43,947 psi | 66% | 2851 fps | 100% |
| Norma 217 | <<locked>> | 80% | 33,417 psi | 50% | 2717 fps | 98% |
| Norma MRP | <<locked>> | 80% | 54,955 psi | 82% | 3146 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 50,386 psi | 76% | 3081 fps | 99.8% |
| Ramshot Magnum | <<locked>> | 80% | 45,513 psi | 68% | 2943 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,501 psi | 44% | 1896 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 43,250 psi | 65% | 2989 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 39,711 psi | 60% | 2871 fps | 96.9% |
| Rottweil R 904 | <<locked>> | 80% | 55,259 psi | 83% | 3091 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 54,621 psi | 82% | 3104 fps | 100% |
| SNPE Vectan SP 13 | <<locked>> | 94% | 45,948 psi | 69% | 2949 fps | 96% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 54,259 psi | 81% | 3097 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 56,521 psi | 85% | 3074 fps | 99.9% |
| Somchem S385 | <<locked>> | 80% | 54,969 psi | 82% | 3068 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 48,240 psi | 72% | 2943 fps | 100% |
| Vihtavuori N170 | <<locked>> | 84% | 47,892 psi | 72% | 2963 fps | 95.9% |
| Vihtavuori N555 | <<locked>> | 80% | 54,795 psi | 82% | 3068 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 54,215 psi | 81% | 3153 fps | 99.8% |
| Vihtavuori N565 | <<locked>> | 80% | 45,527 psi | 68% | 2959 fps | 98.9% |
| Vihtavuori N568 | <<locked>> | 80% | 40,596 psi | 61% | 2887 fps | 96.6% |
| Vihtavuori N570 | 91.8 gr | 84% | 45,020 psi | 67% | 3022 fps | 96.1% |
| Winchester StaBALL HD | <<locked>> | 80% | 50,633 psi | 76% | 3071 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 51,082 psi | 77% | 3005 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 50 powders for 7.21 Firebird loaded with the .284 | 150gr | Sierra GameKing. ADI AR 2218 delivers the highest muzzle velocity at 3,333 fps; across all powders the maximum-charge window runs from 2,067 fps to 3,333 fps. Accurate 8700 gives the best case fill at 100 %, and 50 of the 50 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 150.0 gr projectile in 0.284" calls for a 1:12.0 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, Hodgdon Retumbo, Vihtavuori N570 rank at the top here: for 7.21 Firebird with the .284 | 150gr | Sierra 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.