Load Specifications
Load data in caliber 7.21 Firebird with .284 | 160gr | Speer Grand Slam bullet and 46 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-50.
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.
A valid access license is required to use the Personalized Load Calculator.
You can find more information in our FAQ: How can I use the Personalized Load Calculator?
Max Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 82% | 56,724 psi | 85% | 2986 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 58,233 psi | 87% | 3114 fps | 99.3% |
| Accurate MAGPRO | <<locked>> | 82% | 60,336 psi | 90% | 3173 fps | 100% |
| ADI AR 2213 | <<locked>> | 82% | 56,623 psi | 85% | 3097 fps | 100% |
| ADI AR 2217 | <<locked>> | 90% | 56,840 psi | 85% | 3087 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 58,030 psi | 87% | 3235 fps | 99.8% |
| ADI AR 2225 | <<locked>> | 92% | 57,101 psi | 86% | 3110 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 82% | 57,261 psi | 86% | 3091 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 59,364 psi | 89% | 3038 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 86% | 56,840 psi | 85% | 3071 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 60,307 psi | 90% | 3205 fps | 99.7% |
| Alliant Reloder-50 | <<locked>> | 94% | 56,579 psi | 85% | 3133 fps | 99.1% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 60,220 psi | 90% | 3117 fps | 99.8% |
| Bofors RP15 | <<locked>> | 84% | 56,855 psi | 85% | 3084 fps | 100% |
| Bofors RP30 | <<locked>> | 88% | 56,840 psi | 85% | 3100 fps | 100% |
| Bofors RP5 | <<locked>> | 82% | 57,261 psi | 86% | 3091 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 58,030 psi | 87% | 3104 fps | 100% |
| Hodgdon H4831 | <<locked>> | 82% | 58,595 psi | 88% | 3084 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 57,667 psi | 86% | 3068 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 86% | 57,058 psi | 86% | 3173 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,159 psi | 57% | 2005 fps | 100% |
| Hodgdon US 869 | <<locked>> | 98% | 58,740 psi | 88% | 3117 fps | 96.2% |
| IMR 4955 Enduron | <<locked>> | 82% | 58,363 psi | 87% | 3054 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 59,321 psi | 89% | 3146 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 88% | 57,159 psi | 86% | 3015 fps | 97.2% |
| IMR 8133 Enduron | <<locked>> | 96% | 59,944 psi | 90% | 3159 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 59,292 psi | 89% | 3074 fps | 96.8% |
| Lovex S071 | <<locked>> | 88% | 59,132 psi | 89% | 3018 fps | 100% |
| Norma 217 | <<locked>> | 94% | 57,827 psi | 87% | 3123 fps | 100% |
| Ramshot Grand | <<locked>> | 82% | 56,985 psi | 85% | 3107 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 57,334 psi | 86% | 3153 fps | 96.1% |
| Ramshot Magnum | <<locked>> | 86% | 59,770 psi | 90% | 3091 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,276 psi | 59% | 2054 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 58,044 psi | 87% | 3156 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 88% | 56,898 psi | 85% | 3133 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 59,292 psi | 89% | 3074 fps | 96.8% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 59,538 psi | 89% | 3117 fps | 99.2% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 52,939 psi | 79% | 3025 fps | 96.9% |
| Vihtavuori 24N41 | <<locked>> | 96% | 59,132 psi | 89% | 3123 fps | 96.2% |
| Vihtavuori N165 | <<locked>> | 84% | 57,377 psi | 86% | 3012 fps | 100% |
| Vihtavuori N170 | <<locked>> | 88% | 57,116 psi | 86% | 3058 fps | 98.5% |
| Vihtavuori N565 | <<locked>> | 86% | 58,624 psi | 88% | 3114 fps | 100% |
| Vihtavuori N568 | <<locked>> | 88% | 57,072 psi | 86% | 3133 fps | 99.9% |
| Vihtavuori N570 | <<locked>> | 90% | 58,929 psi | 88% | 3209 fps | 99.4% |
| Winchester StaBALL HD | <<locked>> | 82% | 57,537 psi | 86% | 3084 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 82% | 56,942 psi | 85% | 3018 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% | 53,214 psi | 80% | 2930 fps | 100% |
| Accurate 8700 | <<locked>> | 90% | 40,219 psi | 60% | 2776 fps | 95.1% |
| Accurate MAGPRO | <<locked>> | 80% | 56,101 psi | 84% | 3104 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 80% | 52,823 psi | 79% | 3035 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 39,798 psi | 60% | 2776 fps | 98.9% |
| ADI AR 2218 | 93.6 gr | 84% | 39,827 psi | 60% | 2858 fps | 95.6% |
| ADI AR 2225 | <<locked>> | 80% | 37,246 psi | 56% | 2753 fps | 99.9% |
| Alliant Reloder-22 | <<locked>> | 80% | 53,534 psi | 80% | 3031 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 52,069 psi | 78% | 2933 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 46,369 psi | 70% | 2904 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 82% | 41,408 psi | 62% | 2848 fps | 96% |
| Alliant Reloder-50 | 97.3 gr | 86% | 42,134 psi | 63% | 2851 fps | 95.7% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 49,530 psi | 74% | 2936 fps | 98.5% |
| Bofors RP15 | <<locked>> | 80% | 49,734 psi | 75% | 2966 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 43,410 psi | 65% | 2858 fps | 99.4% |
| Bofors RP5 | <<locked>> | 80% | 53,534 psi | 80% | 3031 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 43,569 psi | 65% | 2854 fps | 99.7% |
| Hodgdon H4831 | <<locked>> | 80% | 54,824 psi | 82% | 3022 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 53,940 psi | 81% | 3009 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 80% | 45,905 psi | 69% | 2986 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,761 psi | 43% | 1801 fps | 100% |
| Hodgdon US 869 | <<locked>> | 96% | 54,607 psi | 82% | 3048 fps | 95.2% |
| IMR 4955 Enduron | <<locked>> | 80% | 54,737 psi | 82% | 2995 fps | 100% |
| IMR 7828 SSC | <<locked>> | 80% | 51,634 psi | 77% | 3022 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 84% | 50,299 psi | 75% | 2894 fps | 95.7% |
| IMR 8133 Enduron | <<locked>> | 80% | 34,693 psi | 52% | 2667 fps | 97.1% |
| Lovex D100 | <<locked>> | 90% | 55,288 psi | 83% | 3012 fps | 95.9% |
| Lovex S071 | <<locked>> | 80% | 45,890 psi | 69% | 2808 fps | 100% |
| Norma 217 | <<locked>> | 80% | 35,505 psi | 53% | 2697 fps | 99.1% |
| Ramshot Grand | <<locked>> | 80% | 53,040 psi | 80% | 3045 fps | 100% |
| Ramshot LRT | <<locked>> | 92% | 53,359 psi | 80% | 3084 fps | 95% |
| Ramshot Magnum | <<locked>> | 80% | 47,892 psi | 72% | 2904 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,544 psi | 44% | 1841 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 45,934 psi | 69% | 2959 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 42,061 psi | 63% | 2854 fps | 98.2% |
| Shooters World 50 BMG | <<locked>> | 90% | 55,288 psi | 83% | 3012 fps | 95.9% |
| SNPE Vectan SP 13 | <<locked>> | 90% | 42,308 psi | 63% | 2802 fps | 95.5% |
| Vihtavuori 20N29 | <<locked>> | 98% | 49,240 psi | 74% | 2956 fps | 95.9% |
| Vihtavuori 24N41 | <<locked>> | 94% | 55,056 psi | 83% | 3054 fps | 95.2% |
| Vihtavuori N165 | <<locked>> | 80% | 50,444 psi | 76% | 2900 fps | 100% |
| Vihtavuori N170 | <<locked>> | 80% | 43,584 psi | 65% | 2802 fps | 95.3% |
| Vihtavuori N565 | <<locked>> | 80% | 47,732 psi | 72% | 2930 fps | 99.6% |
| Vihtavuori N568 | <<locked>> | 80% | 42,830 psi | 64% | 2867 fps | 97.9% |
| Vihtavuori N570 | 87.3 gr | 80% | 41,060 psi | 62% | 2858 fps | 95.4% |
| Winchester StaBALL HD | <<locked>> | 80% | 53,563 psi | 80% | 3028 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 53,214 psi | 80% | 2963 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 | Speer Grand Slam. ADI AR 2218 delivers the highest muzzle velocity at 3,235 fps; across all powders the maximum-charge window runs from 2,005 fps to 3,235 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 1:13.0 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-50 rank at the top here: for 7.21 Firebird with the .284 | 160gr | Speer Grand Slam 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.