Load Specifications
Load data in caliber 7.21 Firebird with .284 | 160gr | Barnes MRX BT bullet and 53 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 IMR 8133 Enduron.
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% | 58,856 psi | 88% | 3018 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 56,217 psi | 84% | 3087 fps | 99.1% |
| Accurate MAGPRO | <<locked>> | 82% | 58,566 psi | 88% | 3146 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 59,770 psi | 90% | 3114 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 59,045 psi | 89% | 3140 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 59,277 psi | 89% | 3127 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 56,028 psi | 84% | 3205 fps | 99.6% |
| ADI AR 2225 | <<locked>> | 94% | 59,350 psi | 89% | 3146 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 59,321 psi | 89% | 3100 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 59,437 psi | 89% | 3127 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 57,769 psi | 87% | 3022 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 59,059 psi | 89% | 3107 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 58,175 psi | 87% | 3176 fps | 99.5% |
| Alliant Reloder-50 | <<locked>> | 96% | 58,552 psi | 88% | 3169 fps | 99.3% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 58,943 psi | 88% | 3100 fps | 99.6% |
| Bofors RP15 | <<locked>> | 86% | 58,987 psi | 88% | 3120 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 58,914 psi | 88% | 3136 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 59,437 psi | 89% | 3127 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 56,333 psi | 84% | 3084 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 57,261 psi | 86% | 3064 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 84% | 60,118 psi | 90% | 3110 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 59,364 psi | 89% | 3212 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,072 psi | 57% | 2005 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,000 psi | 85% | 3038 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 57,827 psi | 87% | 3127 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 59,698 psi | 89% | 3061 fps | 97.7% |
| IMR 8133 Enduron | <<locked>> | 96% | 57,986 psi | 87% | 3136 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 57,711 psi | 87% | 3054 fps | 96.4% |
| Lovex S071 | <<locked>> | 88% | 57,319 psi | 86% | 2999 fps | 100% |
| Norma 217 | <<locked>> | 96% | 59,669 psi | 89% | 3153 fps | 100% |
| Norma MRP | <<locked>> | 82% | 59,857 psi | 90% | 3140 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 59,553 psi | 89% | 3150 fps | 100% |
| Ramshot LRT | <<locked>> | 96% | 59,756 psi | 90% | 3199 fps | 96.6% |
| Ramshot Magnum | <<locked>> | 86% | 57,899 psi | 87% | 3068 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,160 psi | 59% | 2051 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 56,043 psi | 84% | 3130 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 59,161 psi | 89% | 3173 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 59,756 psi | 90% | 3081 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 59,364 psi | 89% | 3097 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 57,711 psi | 87% | 3054 fps | 96.4% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 57,711 psi | 87% | 3094 fps | 99% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,001 psi | 88% | 3094 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 59,277 psi | 89% | 3054 fps | 100% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 50,879 psi | 76% | 2992 fps | 96.4% |
| Vihtavuori N165 | <<locked>> | 86% | 59,828 psi | 90% | 3048 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 59,451 psi | 89% | 3097 fps | 98.8% |
| Vihtavuori N555 | <<locked>> | 82% | 59,088 psi | 89% | 3048 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 59,045 psi | 89% | 3153 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 56,739 psi | 85% | 3091 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 59,350 psi | 89% | 3176 fps | 100% |
| Vihtavuori N570 | <<locked>> | 90% | 57,029 psi | 85% | 3182 fps | 99.2% |
| Winchester StaBALL HD | <<locked>> | 84% | 59,770 psi | 90% | 3120 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 59,466 psi | 89% | 3061 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% | 51,285 psi | 77% | 2907 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 41,611 psi | 62% | 2812 fps | 95.6% |
| Accurate MAGPRO | <<locked>> | 80% | 54,505 psi | 82% | 3081 fps | 99.8% |
| ADI AR 2209 | <<locked>> | 80% | 55,985 psi | 84% | 3054 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 51,256 psi | 77% | 3012 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 38,348 psi | 57% | 2746 fps | 98.5% |
| ADI AR 2218 | 95.2 gr | 86% | 41,249 psi | 62% | 2897 fps | 96.1% |
| ADI AR 2225 | <<locked>> | 80% | 35,708 psi | 54% | 2720 fps | 99.7% |
| Alliant Reloder-19 | <<locked>> | 80% | 55,492 psi | 83% | 3045 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 51,866 psi | 78% | 3005 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 50,502 psi | 76% | 2913 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 44,802 psi | 67% | 2877 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 39,610 psi | 59% | 2808 fps | 95.3% |
| Alliant Reloder-50 | <<locked>> | 88% | 43,149 psi | 65% | 2877 fps | 96% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 48,269 psi | 72% | 2913 fps | 98.2% |
| Bofors RP15 | <<locked>> | 80% | 48,240 psi | 72% | 2943 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 41,611 psi | 62% | 2825 fps | 99.1% |
| Bofors RP5 | <<locked>> | 80% | 51,866 psi | 78% | 3005 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 41,930 psi | 63% | 2828 fps | 99.5% |
| Hodgdon H4831 | <<locked>> | 80% | 53,476 psi | 80% | 3002 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 52,431 psi | 79% | 2986 fps | 99.8% |
| Hodgdon Retumbo | <<locked>> | 80% | 44,222 psi | 66% | 2956 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,601 psi | 43% | 1795 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 53,534 psi | 80% | 2982 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 50,140 psi | 75% | 2995 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 84% | 48,965 psi | 73% | 2874 fps | 95.3% |
| IMR 8133 Enduron | 81.3 gr | 80% | 33,040 psi | 50% | 2625 fps | 96.3% |
| Lovex D100 | <<locked>> | 90% | 53,548 psi | 80% | 2982 fps | 95.4% |
| Lovex S071 | <<locked>> | 80% | 44,135 psi | 66% | 2782 fps | 100% |
| Norma 217 | <<locked>> | 80% | 33,736 psi | 51% | 2657 fps | 98.6% |
| Norma MRP | <<locked>> | 80% | 55,695 psi | 83% | 3077 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 51,242 psi | 77% | 3018 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 55,506 psi | 83% | 3127 fps | 95.6% |
| Ramshot Magnum | <<locked>> | 80% | 46,079 psi | 69% | 2877 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,486 psi | 44% | 1841 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 44,048 psi | 66% | 2927 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 40,321 psi | 60% | 2815 fps | 97.7% |
| Rottweil R 904 | <<locked>> | 80% | 56,072 psi | 84% | 3025 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 55,434 psi | 83% | 3038 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 53,548 psi | 80% | 2982 fps | 95.4% |
| SNPE Vectan SP 13 | <<locked>> | 92% | 43,526 psi | 65% | 2831 fps | 95.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 55,085 psi | 83% | 3031 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 55,463 psi | 83% | 2999 fps | 100% |
| Vihtavuori 20N29 | <<locked>> | 98% | 47,355 psi | 71% | 2923 fps | 95.3% |
| Vihtavuori N165 | <<locked>> | 80% | 48,849 psi | 73% | 2877 fps | 100% |
| Vihtavuori N170 | <<locked>> | 82% | 45,063 psi | 68% | 2835 fps | 95.7% |
| Vihtavuori N555 | <<locked>> | 80% | 55,390 psi | 83% | 2995 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 54,984 psi | 82% | 3087 fps | 100% |
| Vihtavuori N565 | <<locked>> | 80% | 46,064 psi | 69% | 2900 fps | 99.4% |
| Vihtavuori N568 | <<locked>> | 80% | 41,191 psi | 62% | 2835 fps | 97.4% |
| Vihtavuori N570 | 88.9 gr | 82% | 42,409 psi | 64% | 2890 fps | 95.8% |
| Winchester StaBALL HD | <<locked>> | 80% | 51,445 psi | 77% | 2999 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 51,648 psi | 77% | 2940 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 56 powders for 7.21 Firebird loaded with the .284 | 160gr | Barnes MRX BT. Hodgdon Retumbo delivers the highest muzzle velocity at 3,212 fps; across all powders the maximum-charge window runs from 2,005 fps to 3,212 fps. Accurate 8700 gives the best case fill at 100 %, and 56 of the 56 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 1:12.0 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, Vihtavuori N570, IMR 8133 Enduron rank at the top here: for 7.21 Firebird with the .284 | 160gr | Barnes MRX BT 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.