Load Specifications
Load data in caliber 7.21 Firebird with .284 | 100gr | Sierra VarmintKing bullet and 69 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Hodgdon Retumbo, ReloadSwiss RS 76 and Vihtavuori N560.
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>> | 90% | 57,116 psi | 86% | 3563 fps | 100% |
| Accurate 4350 | <<locked>> | 82% | 57,029 psi | 85% | 3609 fps | 100% |
| Accurate MAGPRO | <<locked>> | 88% | 56,275 psi | 84% | 3661 fps | 97.5% |
| ADI AR 2209 | <<locked>> | 88% | 58,349 psi | 87% | 3671 fps | 99.4% |
| ADI AR 2213 | <<locked>> | 90% | 56,884 psi | 85% | 3671 fps | 98.5% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 59,785 psi | 90% | 3704 fps | 99.4% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 54,476 psi | 82% | 3648 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 84% | 58,015 psi | 87% | 3678 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 88% | 57,841 psi | 87% | 3655 fps | 99.3% |
| Alliant Reloder-22 | <<locked>> | 90% | 57,276 psi | 86% | 3671 fps | 99.4% |
| Alliant Reloder-23 | <<locked>> | 92% | 58,827 psi | 88% | 3638 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 96% | 59,509 psi | 89% | 3711 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 88% | 60,336 psi | 90% | 3740 fps | 100% |
| Alliant Reloder-33ᴾ | <<locked>> | 100% | 58,668 psi | 88% | 3711 fps | 96.4% |
| Baschieri & Pellagri 109 | <<locked>> | 92% | 57,957 psi | 87% | 3612 fps | 96.5% |
| Bofors RP15 | <<locked>> | 94% | 60,307 psi | 90% | 3717 fps | 99.6% |
| Bofors RP30 | <<locked>> | 98% | 59,364 psi | 89% | 3711 fps | 99.3% |
| Bofors RP5 | <<locked>> | 90% | 57,276 psi | 86% | 3671 fps | 99.4% |
| Bofors RP7 | <<locked>> | 82% | 58,189 psi | 87% | 3612 fps | 99.7% |
| Hodgdon H1000 | <<locked>> | 96% | 57,348 psi | 86% | 3661 fps | 99.4% |
| Hodgdon H414 | <<locked>> | 82% | 58,465 psi | 88% | 3665 fps | 99.9% |
| Hodgdon H4831 | <<locked>> | 90% | 60,089 psi | 90% | 3668 fps | 98.5% |
| Hodgdon H4831 SC | <<locked>> | 90% | 58,958 psi | 88% | 3648 fps | 98.3% |
| Hodgdon Hybrid 100V | <<locked>> | 86% | 58,305 psi | 87% | 3583 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 58,291 psi | 87% | 3799 fps | 100% |
| Hodgdon Superformance | <<locked>> | 82% | 60,205 psi | 90% | 3704 fps | 99.9% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,318 psi | 56% | 2461 fps | 100% |
| IMR 4350 | <<locked>> | 84% | 56,840 psi | 85% | 3589 fps | 99.7% |
| IMR 4451 Enduron | <<locked>> | 82% | 59,408 psi | 89% | 3635 fps | 99.9% |
| IMR 4831 | <<locked>> | 84% | 57,392 psi | 86% | 3596 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 90% | 60,321 psi | 90% | 3648 fps | 98.7% |
| IMR 7828 SSC | <<locked>> | 92% | 59,030 psi | 88% | 3720 fps | 98.9% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 49,603 psi | 74% | 3527 fps | 97.5% |
| Lovex S065 | <<locked>> | 82% | 56,942 psi | 85% | 3573 fps | 100% |
| Lovex S070 | <<locked>> | 84% | 59,103 psi | 89% | 3629 fps | 100% |
| Lovex S071 | <<locked>> | 96% | 58,798 psi | 88% | 3593 fps | 100% |
| Norma 204 | <<locked>> | 84% | 58,436 psi | 88% | 3652 fps | 99.3% |
| Norma 217ᴾ | <<locked>> | 100% | 50,444 psi | 76% | 3560 fps | 99.3% |
| Norma MRP | <<locked>> | 88% | 57,435 psi | 86% | 3691 fps | 99.9% |
| Norma URP | <<locked>> | 84% | 59,030 psi | 88% | 3652 fps | 100% |
| Ramshot Grand | <<locked>> | 90% | 56,144 psi | 84% | 3668 fps | 98.8% |
| Ramshot Hunter | <<locked>> | 84% | 58,349 psi | 87% | 3652 fps | 100% |
| Ramshot Magnum | <<locked>> | 94% | 59,625 psi | 89% | 3658 fps | 99.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,174 psi | 57% | 2516 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 82% | 57,551 psi | 86% | 3629 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 82% | 56,130 psi | 84% | 3655 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 55,666 psi | 83% | 3707 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 98% | 59,959 psi | 90% | 3730 fps | 98.5% |
| Rottweil R 904 | <<locked>> | 88% | 58,943 psi | 88% | 3635 fps | 98.8% |
| Rottweil R 905 | <<locked>> | 88% | 57,551 psi | 86% | 3645 fps | 99.4% |
| Rottweil R 907 | <<locked>> | 82% | 58,189 psi | 87% | 3612 fps | 99.7% |
| Shooters World Long Rifle | <<locked>> | 82% | 56,942 psi | 85% | 3573 fps | 100% |
| Shooters World SW4350 | <<locked>> | 84% | 59,103 psi | 89% | 3629 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 59,915 psi | 90% | 3576 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 88% | 57,145 psi | 86% | 3638 fps | 99.3% |
| Somchem S361 | <<locked>> | 86% | 57,159 psi | 86% | 3547 fps | 98.1% |
| Somchem S365 | <<locked>> | 84% | 56,550 psi | 85% | 3589 fps | 100% |
| Somchem S385 | <<locked>> | 88% | 58,117 psi | 87% | 3609 fps | 99.8% |
| Vihtavuori N160 | <<locked>> | 82% | 56,724 psi | 85% | 3576 fps | 100% |
| Vihtavuori N165 | <<locked>> | 92% | 58,160 psi | 87% | 3586 fps | 99.7% |
| Vihtavuori N550 | <<locked>> | 84% | 60,147 psi | 90% | 3642 fps | 100% |
| Vihtavuori N555 | <<locked>> | 88% | 56,855 psi | 85% | 3615 fps | 100% |
| Vihtavuori N560 | <<locked>> | 88% | 56,855 psi | 85% | 3681 fps | 98.1% |
| Vihtavuori N565 | <<locked>> | 94% | 57,885 psi | 87% | 3661 fps | 98.6% |
| Vihtavuori N568 | <<locked>> | 98% | 59,973 psi | 90% | 3734 fps | 98% |
| Winchester 6.5 StaBALL | <<locked>> | 82% | 56,768 psi | 85% | 3510 fps | 100% |
| Winchester 760 | <<locked>> | 82% | 58,624 psi | 88% | 3671 fps | 99.9% |
| Winchester StaBALL HD | <<locked>> | 92% | 59,030 psi | 88% | 3734 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 58,262 psi | 87% | 3602 fps | 99.4% |
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% | 40,147 psi | 60% | 3219 fps | 97.9% |
| Accurate 4350 | <<locked>> | 80% | 53,113 psi | 80% | 3540 fps | 100% |
| Accurate MAGPRO | <<locked>> | 84% | 48,443 psi | 73% | 3501 fps | 95.4% |
| ADI AR 2209 | <<locked>> | 80% | 44,164 psi | 66% | 3379 fps | 96.6% |
| ADI AR 2213 | <<locked>> | 84% | 45,730 psi | 69% | 3442 fps | 95.9% |
| ADI AR 2217 | <<locked>> | 92% | 44,846 psi | 67% | 3396 fps | 96.2% |
| ADI AR 2225 | <<locked>> | 88% | 35,578 psi | 53% | 3189 fps | 95.7% |
| Alliant Reloder-16 | <<locked>> | 80% | 50,662 psi | 76% | 3547 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 44,106 psi | 66% | 3369 fps | 96.6% |
| Alliant Reloder-22 | <<locked>> | 80% | 40,176 psi | 60% | 3294 fps | 95.3% |
| Alliant Reloder-23 | <<locked>> | 80% | 38,696 psi | 58% | 3248 fps | 99.8% |
| Alliant Reloder-25 | <<locked>> | 80% | 33,547 psi | 50% | 3130 fps | 96.4% |
| Alliant Reloder-26 | <<locked>> | 80% | 44,121 psi | 66% | 3428 fps | 99.6% |
| Alliant Reloder-33 | <<locked>> | 98% | 54,143 psi | 81% | 3622 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 90% | 54,172 psi | 81% | 3540 fps | 95.5% |
| Bofors RP15 | <<locked>> | 82% | 39,929 psi | 60% | 3284 fps | 95.1% |
| Bofors RP30 | <<locked>> | 88% | 41,510 psi | 62% | 3330 fps | 95% |
| Bofors RP5 | <<locked>> | 80% | 40,176 psi | 60% | 3294 fps | 95.3% |
| Bofors RP7 | <<locked>> | 80% | 54,404 psi | 82% | 3543 fps | 99.4% |
| Hodgdon H1000 | <<locked>> | 88% | 42,699 psi | 64% | 3350 fps | 96% |
| Hodgdon H414 | <<locked>> | 80% | 54,607 psi | 82% | 3596 fps | 99.7% |
| Hodgdon H4831 | <<locked>> | 82% | 45,382 psi | 68% | 3373 fps | 95.1% |
| Hodgdon H4831 SC | <<locked>> | 84% | 47,761 psi | 72% | 3428 fps | 95.8% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 47,587 psi | 71% | 3399 fps | 100% |
| Hodgdon Retumbo | 91.9 gr | 84% | 37,768 psi | 57% | 3310 fps | 95% |
| Hodgdon Superformance | <<locked>> | 80% | 55,782 psi | 84% | 3625 fps | 99.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,847 psi | 42% | 2218 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 49,908 psi | 75% | 3455 fps | 98.9% |
| IMR 4451 Enduron | <<locked>> | 80% | 55,796 psi | 84% | 3573 fps | 99.7% |
| IMR 4831 | <<locked>> | 80% | 50,198 psi | 75% | 3468 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 46,354 psi | 69% | 3369 fps | 95.6% |
| IMR 7828 SSC | <<locked>> | 84% | 44,193 psi | 66% | 3409 fps | 95.4% |
| IMR 8133 Enduron | <<locked>> | 96% | 43,018 psi | 64% | 3376 fps | 95.5% |
| Lovex S065 | <<locked>> | 80% | 53,272 psi | 80% | 3507 fps | 99.9% |
| Lovex S070 | <<locked>> | 80% | 51,880 psi | 78% | 3497 fps | 99.5% |
| Lovex S071 | <<locked>> | 80% | 34,389 psi | 52% | 3061 fps | 95.9% |
| Norma 204 | <<locked>> | 80% | 50,749 psi | 76% | 3504 fps | 98.1% |
| Norma 217 | <<locked>> | 92% | 37,579 psi | 56% | 3255 fps | 95.7% |
| Norma MRP | <<locked>> | 80% | 42,627 psi | 64% | 3379 fps | 97.6% |
| Norma URP | <<locked>> | 80% | 51,605 psi | 77% | 3524 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 44,483 psi | 67% | 3422 fps | 96% |
| Ramshot Hunter | <<locked>> | 80% | 50,778 psi | 76% | 3510 fps | 99.7% |
| Ramshot Magnum | <<locked>> | 82% | 37,057 psi | 56% | 3182 fps | 95.3% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,543 psi | 43% | 2270 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 53,563 psi | 80% | 3560 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 52,054 psi | 78% | 3579 fps | 100% |
| ReloadSwiss RS 76 | 96 gr | 82% | 34,780 psi | 52% | 3192 fps | 95% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 47,239 psi | 71% | 3474 fps | 95.4% |
| Rottweil R 904 | <<locked>> | 80% | 45,092 psi | 68% | 3353 fps | 95.8% |
| Rottweil R 905 | <<locked>> | 80% | 43,613 psi | 65% | 3356 fps | 96.6% |
| Rottweil R 907 | <<locked>> | 80% | 54,404 psi | 82% | 3543 fps | 99.4% |
| Shooters World Long Rifle | <<locked>> | 80% | 53,272 psi | 80% | 3507 fps | 99.9% |
| Shooters World SW4350 | <<locked>> | 80% | 51,880 psi | 78% | 3497 fps | 99.5% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 52,359 psi | 78% | 3445 fps | 99.5% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 43,279 psi | 65% | 3350 fps | 96.5% |
| Somchem S361 | <<locked>> | 80% | 46,354 psi | 69% | 3330 fps | 95.5% |
| Somchem S365 | <<locked>> | 80% | 49,168 psi | 74% | 3465 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 44,222 psi | 66% | 3330 fps | 97.6% |
| Vihtavuori N160 | <<locked>> | 80% | 52,968 psi | 79% | 3514 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 38,377 psi | 58% | 3166 fps | 95.4% |
| Vihtavuori N550 | <<locked>> | 80% | 52,489 psi | 79% | 3510 fps | 100% |
| Vihtavuori N555 | <<locked>> | 80% | 43,134 psi | 65% | 3346 fps | 99.7% |
| Vihtavuori N560 | 93.1 gr | 82% | 45,716 psi | 69% | 3445 fps | 95.2% |
| Vihtavuori N565 | <<locked>> | 88% | 46,775 psi | 70% | 3432 fps | 96% |
| Vihtavuori N568 | <<locked>> | 92% | 47,950 psi | 72% | 3494 fps | 95% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 52,924 psi | 79% | 3448 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 54,766 psi | 82% | 3599 fps | 99.7% |
| Winchester StaBALL HD | <<locked>> | 80% | 36,318 psi | 54% | 3274 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 40,640 psi | 61% | 3235 fps | 95.6% |
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 74 powders for 7.21 Firebird loaded with the .284 | 100gr | Sierra VarmintKing. Hodgdon Retumbo delivers the highest muzzle velocity at 3,799 fps; across all powders the maximum-charge window runs from 2,461 fps to 3,799 fps. ADI AR 2217 gives the best case fill at 100 %, and 74 of the 74 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (460 MPa), the top charges use 56–90 %, leaving at least 10 % headroom. The 100.0 gr projectile in 0.284" calls for a 1:15.0 twist; slower twists will usually not stabilise this weight. ADI AR 2217, ADI AR 2218, ADI AR 2225 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. Hodgdon Retumbo, ReloadSwiss RS 76, Vihtavuori N560 rank at the top here: for 7.21 Firebird with the .284 | 100gr | Sierra VarmintKing they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, ADI AR 2218, Alliant Reloder-50, IMR 7977 Enduron 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.