Load Specifications
Load data in caliber 7.21 Firebird with .284 | 160gr | Winchester Silvertip bullet and 43 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 Alliant Reloder-33.
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>> | 82% | 58,160 psi | 87% | 3002 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 60,249 psi | 90% | 3143 fps | 99.6% |
| ADI AR 2213 | <<locked>> | 82% | 58,117 psi | 87% | 3120 fps | 100% |
| ADI AR 2217 | <<locked>> | 90% | 58,436 psi | 88% | 3110 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 60,075 psi | 90% | 3264 fps | 99.9% |
| ADI AR 2225 | <<locked>> | 92% | 58,900 psi | 88% | 3130 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 58,682 psi | 88% | 3110 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 82% | 57,043 psi | 86% | 3005 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 86% | 58,552 psi | 88% | 3094 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 90% | 57,725 psi | 87% | 3159 fps | 99.5% |
| Alliant Reloder-50 | <<locked>> | 94% | 58,711 psi | 88% | 3166 fps | 99.4% |
| Baschieri & Pellagri 109 | <<locked>> | 84% | 57,696 psi | 86% | 3077 fps | 99.6% |
| Bofors RP15 | <<locked>> | 84% | 58,262 psi | 87% | 3104 fps | 100% |
| Bofors RP30 | <<locked>> | 88% | 58,436 psi | 88% | 3123 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 58,682 psi | 88% | 3110 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 59,669 psi | 89% | 3127 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 59,973 psi | 90% | 3104 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 59,059 psi | 89% | 3087 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 86% | 58,958 psi | 88% | 3199 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,305 psi | 57% | 2014 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 59,495 psi | 89% | 3071 fps | 100% |
| IMR 7828 SSC | <<locked>> | 82% | 56,869 psi | 85% | 3107 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 58,450 psi | 88% | 3041 fps | 97.6% |
| IMR 8133 Enduron | <<locked>> | 94% | 57,870 psi | 87% | 3127 fps | 100% |
| Lovex D100 | <<locked>> | 90% | 56,768 psi | 85% | 3035 fps | 96.4% |
| Lovex S071 | <<locked>> | 86% | 56,927 psi | 85% | 2986 fps | 100% |
| Norma 217 | <<locked>> | 94% | 59,683 psi | 89% | 3143 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 58,755 psi | 88% | 3130 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 59,146 psi | 89% | 3182 fps | 96.6% |
| Ramshot Magnum | <<locked>> | 84% | 57,116 psi | 86% | 3051 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,407 psi | 59% | 2064 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 59,944 psi | 90% | 3176 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 58,784 psi | 88% | 3156 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 56,768 psi | 85% | 3035 fps | 96.4% |
| SNPE Vectan SP 13 | <<locked>> | 98% | 57,377 psi | 86% | 3081 fps | 99% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 54,795 psi | 82% | 3054 fps | 97.4% |
| Vihtavuori N165 | <<locked>> | 84% | 58,711 psi | 88% | 3028 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 58,581 psi | 88% | 3081 fps | 98.8% |
| Vihtavuori N565 | <<locked>> | 86% | 60,147 psi | 90% | 3136 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 58,769 psi | 88% | 3159 fps | 100% |
| Vihtavuori N570 | <<locked>> | 88% | 56,608 psi | 85% | 3166 fps | 99.2% |
| Winchester StaBALL HD | <<locked>> | 82% | 59,538 psi | 89% | 3107 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 58,276 psi | 87% | 3038 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% | 54,491 psi | 82% | 2949 fps | 100% |
| Accurate 8700 | <<locked>> | 90% | 41,742 psi | 63% | 2805 fps | 95.8% |
| ADI AR 2213 | <<locked>> | 80% | 54,157 psi | 81% | 3058 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 40,973 psi | 61% | 2799 fps | 99.1% |
| ADI AR 2218 | 95.8 gr | 84% | 41,060 psi | 62% | 2887 fps | 96.2% |
| ADI AR 2225 | <<locked>> | 80% | 38,435 psi | 58% | 2772 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 54,853 psi | 82% | 3051 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 53,447 psi | 80% | 2953 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 47,703 psi | 72% | 2923 fps | 100% |
| Alliant Reloder-33 | 92.9 gr | 80% | 39,682 psi | 59% | 2802 fps | 95.4% |
| Alliant Reloder-50 | <<locked>> | 84% | 40,495 psi | 61% | 2808 fps | 95.1% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 50,618 psi | 76% | 2953 fps | 98.8% |
| Bofors RP15 | <<locked>> | 80% | 51,010 psi | 76% | 2986 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 44,643 psi | 67% | 2881 fps | 99.6% |
| Bofors RP5 | <<locked>> | 80% | 54,853 psi | 82% | 3051 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 44,802 psi | 67% | 2877 fps | 99.9% |
| Hodgdon H4831 | <<locked>> | 80% | 56,188 psi | 84% | 3045 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 80% | 55,129 psi | 83% | 3028 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 47,384 psi | 71% | 3009 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,834 psi | 43% | 1808 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 55,883 psi | 84% | 3018 fps | 100% |
| IMR 7828 SSC | <<locked>> | 80% | 52,968 psi | 79% | 3041 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 82% | 48,051 psi | 72% | 2854 fps | 95.2% |
| IMR 8133 Enduron | <<locked>> | 80% | 35,839 psi | 54% | 2694 fps | 97.6% |
| Lovex D100 | <<locked>> | 88% | 52,866 psi | 79% | 2969 fps | 95.5% |
| Lovex S071 | <<locked>> | 80% | 47,007 psi | 70% | 2825 fps | 100% |
| Norma 217 | <<locked>> | 80% | 36,753 psi | 55% | 2723 fps | 99.4% |
| Ramshot Grand | <<locked>> | 80% | 54,418 psi | 82% | 3068 fps | 100% |
| Ramshot LRT | <<locked>> | 92% | 54,984 psi | 82% | 3114 fps | 95.6% |
| Ramshot Magnum | <<locked>> | 80% | 49,269 psi | 74% | 2927 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,631 psi | 44% | 1850 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 47,630 psi | 71% | 2982 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 43,526 psi | 65% | 2881 fps | 98.6% |
| Shooters World 50 BMG | <<locked>> | 88% | 52,866 psi | 79% | 2969 fps | 95.5% |
| SNPE Vectan SP 13 | <<locked>> | 88% | 40,727 psi | 61% | 2762 fps | 95% |
| Vihtavuori 20N29 | <<locked>> | 96% | 47,558 psi | 71% | 2920 fps | 95.6% |
| Vihtavuori N165 | <<locked>> | 80% | 51,619 psi | 77% | 2920 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 44,730 psi | 67% | 2825 fps | 95.8% |
| Vihtavuori N565 | <<locked>> | 80% | 49,110 psi | 74% | 2953 fps | 99.7% |
| Vihtavuori N568 | <<locked>> | 80% | 44,295 psi | 66% | 2894 fps | 98.3% |
| Vihtavuori N570 | 89.4 gr | 80% | 42,409 psi | 64% | 2887 fps | 96% |
| Winchester StaBALL HD | <<locked>> | 80% | 55,317 psi | 83% | 3048 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 54,389 psi | 82% | 2979 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 46 powders for 7.21 Firebird loaded with the .284 | 160gr | Winchester Silvertip. ADI AR 2218 delivers the highest muzzle velocity at 3,264 fps; across all powders the maximum-charge window runs from 2,014 fps to 3,264 fps. Accurate 8700 gives the best case fill at 100 %, and 46 of the 46 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 1:16.0 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, Alliant Reloder-33 rank at the top here: for 7.21 Firebird with the .284 | 160gr | Winchester Silvertip 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.