Load Specifications
Load data in caliber 7.21 Firebird with .284 | 140gr | Barnes MRX BT 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% | 57,899 psi | 87% | 3176 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 50,169 psi | 75% | 3130 fps | 96.8% |
| Accurate MAGPRO | <<locked>> | 84% | 57,319 psi | 86% | 3291 fps | 99.6% |
| ADI AR 2209 | <<locked>> | 84% | 59,045 psi | 89% | 3278 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 57,943 psi | 87% | 3294 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 57,653 psi | 86% | 3274 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 58,740 psi | 88% | 3409 fps | 99.2% |
| ADI AR 2225 | <<locked>> | 96% | 57,290 psi | 86% | 3291 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 58,595 psi | 88% | 3261 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 58,320 psi | 87% | 3281 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 56,478 psi | 85% | 3179 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 57,450 psi | 86% | 3261 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 57,406 psi | 86% | 3268 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 56,405 psi | 85% | 3304 fps | 98.6% |
| Alliant Reloder-50 | <<locked>> | 98% | 56,420 psi | 85% | 3291 fps | 98.1% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 58,421 psi | 88% | 3248 fps | 98.9% |
| Bofors RP15 | <<locked>> | 88% | 57,870 psi | 87% | 3274 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 57,246 psi | 86% | 3278 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 58,320 psi | 87% | 3281 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 59,161 psi | 89% | 3294 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 56,536 psi | 85% | 3215 fps | 99.7% |
| Hodgdon H4831 SC | <<locked>> | 86% | 59,350 psi | 89% | 3261 fps | 99.9% |
| Hodgdon Hybrid 100V | <<locked>> | 82% | 59,016 psi | 88% | 3166 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 57,290 psi | 86% | 3363 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,797 psi | 57% | 2126 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 56,623 psi | 85% | 3192 fps | 99.7% |
| IMR 7828 SSC | <<locked>> | 86% | 56,594 psi | 85% | 3274 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 92% | 59,190 psi | 89% | 3199 fps | 96.3% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 59,886 psi | 90% | 3333 fps | 100% |
| Lovex S071 | <<locked>> | 92% | 59,814 psi | 90% | 3202 fps | 100% |
| Norma 217 | <<locked>> | 98% | 57,319 psi | 86% | 3291 fps | 100% |
| Norma MRP | <<locked>> | 84% | 58,697 psi | 88% | 3297 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 58,102 psi | 87% | 3297 fps | 100% |
| Ramshot Magnum | <<locked>> | 88% | 56,666 psi | 85% | 3219 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,812 psi | 58% | 2175 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 58,436 psi | 88% | 3343 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 57,450 psi | 86% | 3307 fps | 99.7% |
| Rottweil R 904 | <<locked>> | 84% | 59,132 psi | 89% | 3241 fps | 100% |
| Rottweil R 905 | <<locked>> | 84% | 58,378 psi | 88% | 3251 fps | 100% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 52,083 psi | 78% | 3143 fps | 96.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 58,001 psi | 87% | 3251 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 56,942 psi | 85% | 3166 fps | 99.7% |
| Somchem S385 | <<locked>> | 84% | 58,508 psi | 88% | 3212 fps | 100% |
| Vihtavuori N165 | <<locked>> | 88% | 58,943 psi | 88% | 3202 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 58,407 psi | 88% | 3232 fps | 97.6% |
| Vihtavuori N555 | <<locked>> | 84% | 58,073 psi | 87% | 3212 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 57,986 psi | 87% | 3307 fps | 99.8% |
| Vihtavuori N565 | <<locked>> | 90% | 59,335 psi | 89% | 3297 fps | 100% |
| Vihtavuori N568 | <<locked>> | 92% | 57,609 psi | 86% | 3310 fps | 99.5% |
| Vihtavuori N570 | <<locked>> | 94% | 59,335 psi | 89% | 3383 fps | 98.7% |
| Winchester StaBALL HD | <<locked>> | 86% | 57,754 psi | 87% | 3274 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 58,682 psi | 88% | 3212 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% | 46,978 psi | 70% | 2992 fps | 100% |
| Accurate 8700 | <<locked>> | 98% | 46,528 psi | 70% | 3058 fps | 95.8% |
| Accurate MAGPRO | <<locked>> | 80% | 49,603 psi | 74% | 3150 fps | 98.6% |
| ADI AR 2209 | <<locked>> | 80% | 51,416 psi | 77% | 3146 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 46,760 psi | 70% | 3087 fps | 98.9% |
| ADI AR 2217 | <<locked>> | 80% | 34,635 psi | 52% | 2795 fps | 95.7% |
| ADI AR 2218 | 100.2 gr | 90% | 43,105 psi | 65% | 3077 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 80% | 31,966 psi | 48% | 2759 fps | 97.7% |
| Alliant Reloder-19 | <<locked>> | 80% | 51,242 psi | 77% | 3136 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 47,413 psi | 71% | 3087 fps | 99.6% |
| Alliant Reloder-23 | <<locked>> | 80% | 46,093 psi | 69% | 3009 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 40,219 psi | 60% | 2949 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 53,272 psi | 80% | 3202 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 88% | 44,672 psi | 67% | 3071 fps | 95.6% |
| Alliant Reloder-50 | <<locked>> | 92% | 44,657 psi | 67% | 3054 fps | 95% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 44,556 psi | 67% | 2986 fps | 96% |
| Bofors RP15 | <<locked>> | 80% | 44,063 psi | 66% | 3015 fps | 99.1% |
| Bofors RP30 | <<locked>> | 80% | 37,478 psi | 56% | 2874 fps | 96.8% |
| Bofors RP5 | <<locked>> | 80% | 47,413 psi | 71% | 3087 fps | 99.6% |
| Hodgdon H1000 | <<locked>> | 80% | 37,811 psi | 57% | 2881 fps | 97.6% |
| Hodgdon H4831 | <<locked>> | 80% | 49,211 psi | 74% | 3084 fps | 98.8% |
| Hodgdon H4831 SC | <<locked>> | 80% | 48,254 psi | 72% | 3068 fps | 98.7% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 55,303 psi | 83% | 3114 fps | 100% |
| Hodgdon Retumbo | 84.1 gr | 80% | 39,436 psi | 59% | 3009 fps | 99% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,398 psi | 43% | 1909 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 49,617 psi | 74% | 3068 fps | 99% |
| IMR 7828 SSC | <<locked>> | 80% | 45,571 psi | 68% | 3071 fps | 98.7% |
| IMR 7977 Enduron | <<locked>> | 90% | 55,347 psi | 83% | 3136 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 84% | 34,040 psi | 51% | 2795 fps | 95.2% |
| Lovex S071 | <<locked>> | 80% | 40,350 psi | 60% | 2858 fps | 99.8% |
| Norma 217 | <<locked>> | 80% | 29,631 psi | 44% | 2684 fps | 95.4% |
| Norma MRP | <<locked>> | 80% | 50,734 psi | 76% | 3166 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 46,137 psi | 69% | 3084 fps | 99% |
| Ramshot Magnum | <<locked>> | 80% | 41,466 psi | 62% | 2940 fps | 99.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,095 psi | 44% | 1952 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 39,073 psi | 59% | 2979 fps | 99.6% |
| ReloadSwiss RS 80 | <<locked>> | 82% | 38,827 psi | 58% | 2927 fps | 95.8% |
| Rottweil R 904 | <<locked>> | 80% | 51,851 psi | 78% | 3117 fps | 99.5% |
| Rottweil R 905 | <<locked>> | 80% | 50,995 psi | 76% | 3127 fps | 99.9% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 48,356 psi | 72% | 3074 fps | 95.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 50,647 psi | 76% | 3123 fps | 99.9% |
| Somchem S361 | <<locked>> | 80% | 53,040 psi | 80% | 3100 fps | 99.4% |
| Somchem S385 | <<locked>> | 80% | 51,198 psi | 77% | 3094 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 44,904 psi | 67% | 2963 fps | 99.6% |
| Vihtavuori N170 | <<locked>> | 88% | 50,923 psi | 76% | 3097 fps | 95.9% |
| Vihtavuori N555 | <<locked>> | 80% | 50,807 psi | 76% | 3097 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 50,212 psi | 75% | 3166 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 80% | 41,785 psi | 63% | 2959 fps | 97.5% |
| Vihtavuori N568 | <<locked>> | 82% | 39,798 psi | 60% | 2949 fps | 95.5% |
| Vihtavuori N570 | 96 gr | 88% | 47,558 psi | 71% | 3159 fps | 96.1% |
| Winchester StaBALL HD | <<locked>> | 80% | 45,658 psi | 68% | 3081 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 47,456 psi | 71% | 3022 fps | 99.6% |
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 | 140gr | Barnes MRX BT. ADI AR 2218 delivers the highest muzzle velocity at 3,409 fps; across all powders the maximum-charge window runs from 2,126 fps to 3,409 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 140.0 gr projectile in 0.284" calls for a 1:11.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, 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 | 140gr | Barnes MRX BT they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG, Hodgdon US 869, Lovex D100 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.