Load Specifications
Bullet Manufacturer:Sierra
Bullet Weight:165 gr
Bullet Diameter:0.284"
Bullet Length:<<locked>>
Caliber:7.21 Firebird load data
Case Length (l3):2.8"
Cartridge Length (C.O.L.):<<locked>>
Case Capacity:121 Grains of Water
Primer Size:Large Rifle Magnum (LRM)
Barrel Length:26"
Max. allowed Pressure:66,717 psi
Recommended Twist Rate:1:9.5
Load data in caliber 7.21 Firebird with .284 | 165gr | Sierra Tipped GameKing bullet and 103 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Vihtavuori N570, ADI AR 2218 and Hodgdon H1000.
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>> | 84% | 59,306 psi | 89% | 2922 fps | 100% |
| Accurate 3100 | <<locked>> | 84% | 59,582 psi | 89% | 2986 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 56,304 psi | 84% | 2981 fps | 98.6% |
| Accurate 8700ᴾ | <<locked>> | 100% | 56,478 psi | 85% | 3054 fps | 99.2% |
| Accurate MAGPRO | <<locked>> | 84% | 59,770 psi | 90% | 3123 fps | 100% |
| Accurate MAGPRO | <<locked>> | 82% | 59,016 psi | 88% | 3114 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 59,988 psi | 90% | 3010 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 60,089 psi | 90% | 3074 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 59,103 psi | 89% | 3032 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 59,408 psi | 89% | 3104 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 59,132 psi | 89% | 3020 fps | 100% |
| ADI AR 2217 | <<locked>> | 92% | 59,408 psi | 89% | 3091 fps | 100% |
| ADI AR 2218 | <<locked>> | 94% | 56,057 psi | 84% | 3092 fps | 99.3% |
| ADI AR 2218 | <<locked>> | 94% | 56,333 psi | 84% | 3176 fps | 99.7% |
| ADI AR 2225 | <<locked>> | 94% | 59,480 psi | 89% | 3045 fps | 100% |
| ADI AR 2225 | <<locked>> | 94% | 59,524 psi | 89% | 3110 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 82% | 60,307 psi | 90% | 3071 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 59,422 psi | 89% | 2997 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 59,712 psi | 90% | 3064 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 59,640 psi | 89% | 3023 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 59,915 psi | 90% | 3094 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 58,030 psi | 87% | 2923 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 84% | 58,146 psi | 87% | 2986 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 59,379 psi | 89% | 3006 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 88% | 59,480 psi | 89% | 3071 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 58,363 psi | 87% | 3067 fps | 99.2% |
| Alliant Reloder-33 | <<locked>> | 92% | 58,421 psi | 88% | 3143 fps | 99.6% |
| Alliant Reloder-50 | <<locked>> | 96% | 58,827 psi | 88% | 3065 fps | 99% |
| Alliant Reloder-50 | <<locked>> | 96% | 59,088 psi | 89% | 3146 fps | 99.5% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 58,929 psi | 88% | 2991 fps | 99.4% |
| Baschieri & Pellagri 109 | <<locked>> | 86% | 59,132 psi | 89% | 3064 fps | 99.7% |
| Bofors RP15 | <<locked>> | 86% | 59,219 psi | 89% | 3084 fps | 100% |
| Bofors RP15 | <<locked>> | 86% | 59,306 psi | 89% | 3084 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 59,132 psi | 89% | 3033 fps | 100% |
| Bofors RP30 | <<locked>> | 90% | 59,408 psi | 89% | 3107 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 59,640 psi | 89% | 3087 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 59,915 psi | 90% | 3094 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 56,869 psi | 85% | 3051 fps | 100% |
| Hodgdon H1000 | <<locked>> | 88% | 56,782 psi | 85% | 3048 fps | 100% |
| Hodgdon H4831 | <<locked>> | 86% | 57,696 psi | 86% | 2964 fps | 99.9% |
| Hodgdon H4831 | <<locked>> | 82% | 57,595 psi | 86% | 3028 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 84% | 60,220 psi | 90% | 3003 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 82% | 56,637 psi | 85% | 3015 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 59,466 psi | 89% | 3176 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 88% | 59,770 psi | 90% | 3179 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,928 psi | 58% | 1930 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,101 psi | 57% | 1965 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,246 psi | 86% | 2999 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 82% | 57,348 psi | 86% | 3002 fps | 100% |
| IMR 7828 SSC | <<locked>> | 82% | 57,725 psi | 87% | 3016 fps | 100% |
| IMR 7828 SSC | <<locked>> | 84% | 58,001 psi | 87% | 3087 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 59,828 psi | 90% | 3018 fps | 97.8% |
| IMR 7977 Enduron | <<locked>> | 90% | 59,872 psi | 90% | 3022 fps | 97.8% |
| IMR 8133 Enduron | <<locked>> | 96% | 58,233 psi | 87% | 3032 fps | 100% |
| IMR 8133 Enduron | <<locked>> | 96% | 58,320 psi | 87% | 3104 fps | 100% |
| Lovex D100 | <<locked>> | 92% | 57,856 psi | 87% | 3015 fps | 96.6% |
| Lovex S071 | <<locked>> | 88% | 57,740 psi | 87% | 2900 fps | 100% |
| Lovex S071 | <<locked>> | 88% | 58,015 psi | 87% | 2963 fps | 100% |
| Norma 217 | <<locked>> | 96% | 59,973 psi | 90% | 3051 fps | 100% |
| Norma 217 | <<locked>> | 96% | 60,292 psi | 90% | 3123 fps | 100% |
| Norma MRP | <<locked>> | 82% | 60,118 psi | 90% | 3036 fps | 100% |
| Norma MRP | <<locked>> | 82% | 60,205 psi | 90% | 3104 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 59,944 psi | 90% | 3114 fps | 100% |
| Ramshot LRT | <<locked>> | 96% | 59,901 psi | 90% | 3166 fps | 96.8% |
| Ramshot Magnum | <<locked>> | 84% | 59,538 psi | 89% | 2988 fps | 100% |
| Ramshot Magnum | <<locked>> | 86% | 58,378 psi | 88% | 3035 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,827 psi | 60% | 1976 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,262 psi | 59% | 2011 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 56,115 psi | 84% | 3025 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 86% | 56,420 psi | 85% | 3100 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 59,422 psi | 89% | 3066 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 59,727 psi | 90% | 3143 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 60,002 psi | 90% | 2979 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 60,060 psi | 90% | 3041 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 59,524 psi | 89% | 2991 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 59,611 psi | 89% | 3058 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 57,856 psi | 87% | 3015 fps | 96.6% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 59,161 psi | 89% | 2986 fps | 98.5% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 57,928 psi | 87% | 3058 fps | 99.1% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,146 psi | 89% | 3051 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 59,248 psi | 89% | 3051 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 59,625 psi | 89% | 2956 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 59,886 psi | 90% | 3022 fps | 100% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 58,001 psi | 87% | 2982 fps | 97% |
| Vihtavuori 20N29ᴾ | <<locked>> | 100% | 51,329 psi | 77% | 2966 fps | 96.7% |
| Vihtavuori 24N41 | <<locked>> | 96% | 57,754 psi | 87% | 3068 fps | 96% |
| Vihtavuori N165 | <<locked>> | 86% | 58,160 psi | 87% | 2923 fps | 100% |
| Vihtavuori N165 | <<locked>> | 86% | 60,176 psi | 90% | 3012 fps | 100% |
| Vihtavuori N170 | <<locked>> | 94% | 57,827 psi | 87% | 2962 fps | 98.1% |
| Vihtavuori N170 | <<locked>> | 90% | 59,756 psi | 90% | 3061 fps | 98.9% |
| Vihtavuori N555 | <<locked>> | 82% | 59,611 psi | 89% | 2951 fps | 100% |
| Vihtavuori N555 | <<locked>> | 82% | 59,901 psi | 90% | 3015 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 60,365 psi | 90% | 3067 fps | 100% |
| Vihtavuori N560 | <<locked>> | 82% | 59,364 psi | 89% | 3117 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 57,130 psi | 86% | 2989 fps | 100% |
| Vihtavuori N565 | <<locked>> | 86% | 57,203 psi | 86% | 3058 fps | 100% |
| Vihtavuori N568 | <<locked>> | 90% | 59,611 psi | 89% | 3069 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 90% | 59,698 psi | 89% | 3143 fps | 100% |
| Vihtavuori N570 | <<locked>> | 90% | 57,595 psi | 86% | 3073 fps | 98.9% |
| Vihtavuori N570 | <<locked>> | 90% | 57,334 psi | 86% | 3150 fps | 99.3% |
| Winchester StaBALL HD | <<locked>> | 84% | 60,191 psi | 90% | 3021 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 84% | 60,278 psi | 90% | 3087 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 59,799 psi | 90% | 3022 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% | 51,909 psi | 78% | 2813 fps | 100% |
| Accurate 3100 | <<locked>> | 80% | 52,185 psi | 78% | 2877 fps | 100% |
| Accurate 8700 | <<locked>> | 94% | 45,005 psi | 67% | 2780 fps | 96% |
| Accurate 8700 | <<locked>> | 92% | 41,989 psi | 63% | 2789 fps | 96% |
| Accurate MAGPRO | <<locked>> | 80% | 52,054 psi | 78% | 2995 fps | 99.5% |
| Accurate MAGPRO | <<locked>> | 80% | 54,911 psi | 82% | 3048 fps | 99.9% |
| ADI AR 2209 | <<locked>> | 80% | 56,144 psi | 84% | 2952 fps | 100% |
| ADI AR 2209 | <<locked>> | 80% | 56,231 psi | 84% | 3018 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 51,547 psi | 77% | 2909 fps | 99.8% |
| ADI AR 2213 | <<locked>> | 80% | 51,648 psi | 77% | 2979 fps | 100% |
| ADI AR 2217 | <<locked>> | 80% | 38,841 psi | 58% | 2656 fps | 98.1% |
| ADI AR 2217 | <<locked>> | 80% | 38,957 psi | 58% | 2726 fps | 98.8% |
| ADI AR 2218 | 92 gr | 86% | 41,597 psi | 62% | 2796 fps | 95.4% |
| ADI AR 2218 | 89.9 gr | 84% | 38,754 psi | 58% | 2802 fps | 95.3% |
| ADI AR 2225 | <<locked>> | 80% | 36,216 psi | 54% | 2629 fps | 99.5% |
| ADI AR 2225 | <<locked>> | 80% | 36,303 psi | 54% | 2703 fps | 99.9% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 56,536 psi | 85% | 3015 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 55,724 psi | 84% | 2939 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 55,985 psi | 84% | 3009 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 52,272 psi | 78% | 2907 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 52,359 psi | 78% | 2976 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 50,981 psi | 76% | 2820 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 51,068 psi | 77% | 2884 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 45,179 psi | 68% | 2784 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 45,281 psi | 68% | 2851 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 84% | 43,308 psi | 65% | 2786 fps | 95.9% |
| Alliant Reloder-33 | <<locked>> | 82% | 40,205 psi | 60% | 2792 fps | 95.8% |
| Alliant Reloder-50 | <<locked>> | 88% | 43,714 psi | 66% | 2784 fps | 95.4% |
| Alliant Reloder-50 | <<locked>> | 86% | 40,770 psi | 61% | 2799 fps | 95.5% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 48,486 psi | 73% | 2812 fps | 97.8% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 48,559 psi | 73% | 2884 fps | 98.4% |
| Bofors RP15 | <<locked>> | 80% | 48,733 psi | 73% | 2910 fps | 100% |
| Bofors RP15 | <<locked>> | 80% | 48,834 psi | 73% | 2913 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 42,148 psi | 63% | 2731 fps | 98.8% |
| Bofors RP30 | <<locked>> | 80% | 42,409 psi | 64% | 2808 fps | 99.4% |
| Bofors RP5 | <<locked>> | 80% | 52,272 psi | 78% | 2972 fps | 100% |
| Bofors RP5 | <<locked>> | 80% | 52,359 psi | 78% | 2976 fps | 100% |
| Hodgdon H1000 | 81.1 gr | 80% | 39,943 psi | 60% | 2749 fps | 99.3% |
| Hodgdon H1000 | 81.1 gr | 80% | 42,395 psi | 64% | 2802 fps | 99.7% |
| Hodgdon H4831 | <<locked>> | 80% | 47,500 psi | 71% | 2791 fps | 99% |
| Hodgdon H4831 | <<locked>> | 80% | 53,882 psi | 81% | 2969 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 52,707 psi | 79% | 2886 fps | 99.7% |
| Hodgdon H4831 SC | <<locked>> | 80% | 52,823 psi | 79% | 2953 fps | 99.9% |
| Hodgdon Retumbo | <<locked>> | 80% | 44,585 psi | 67% | 2930 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 80% | 44,715 psi | 67% | 2930 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,718 psi | 43% | 1729 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,747 psi | 43% | 1762 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 53,722 psi | 81% | 2943 fps | 99.9% |
| IMR 4955 Enduron | <<locked>> | 80% | 53,824 psi | 81% | 2943 fps | 100% |
| IMR 7828 SSC | <<locked>> | 80% | 53,679 psi | 80% | 2951 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 50,575 psi | 76% | 2966 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 84% | 49,226 psi | 74% | 2838 fps | 95.5% |
| IMR 7977 Enduron | <<locked>> | 84% | 49,443 psi | 74% | 2844 fps | 95.6% |
| IMR 8133 Enduron | <<locked>> | 80% | 33,736 psi | 51% | 2544 fps | 95.9% |
| IMR 8133 Enduron | <<locked>> | 80% | 33,837 psi | 51% | 2621 fps | 97% |
| Lovex D100 | <<locked>> | 90% | 53,983 psi | 81% | 2953 fps | 95.7% |
| Lovex S071 | <<locked>> | 80% | 44,918 psi | 67% | 2695 fps | 100% |
| Lovex S071 | <<locked>> | 80% | 45,049 psi | 68% | 2759 fps | 100% |
| Norma 217 | <<locked>> | 80% | 34,374 psi | 52% | 2572 fps | 98.3% |
| Norma 217 | <<locked>> | 80% | 34,490 psi | 52% | 2648 fps | 99% |
| Norma MRP | <<locked>> | 80% | 56,057 psi | 84% | 2977 fps | 100% |
| Norma MRP | <<locked>> | 80% | 56,159 psi | 84% | 3045 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 51,822 psi | 78% | 2989 fps | 100% |
| Ramshot LRT | <<locked>> | 94% | 55,825 psi | 84% | 3094 fps | 95.8% |
| Ramshot Magnum | <<locked>> | 80% | 51,242 psi | 77% | 2865 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 46,702 psi | 70% | 2851 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,515 psi | 44% | 1770 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,559 psi | 44% | 1804 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 44,425 psi | 67% | 2829 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 44,686 psi | 67% | 2904 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 40,799 psi | 61% | 2723 fps | 97.2% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 41,031 psi | 62% | 2802 fps | 98.1% |
| Rottweil R 904 | <<locked>> | 80% | 56,202 psi | 84% | 2921 fps | 100% |
| Rottweil R 904 | <<locked>> | 80% | 56,304 psi | 84% | 2986 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 55,680 psi | 83% | 2933 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 55,796 psi | 84% | 2999 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 90% | 53,983 psi | 81% | 2953 fps | 95.7% |
| SNPE Vectan SP 13 | <<locked>> | 92% | 43,801 psi | 66% | 2734 fps | 95.2% |
| SNPE Vectan SP 13 | <<locked>> | 90% | 41,176 psi | 62% | 2749 fps | 95.3% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 55,361 psi | 83% | 2995 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 55,448 psi | 83% | 2995 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 55,912 psi | 84% | 2903 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 56,014 psi | 84% | 2966 fps | 100% |
| Vihtavuori 20N29 | <<locked>> | 96% | 48,834 psi | 73% | 2844 fps | 95% |
| Vihtavuori 20N29 | <<locked>> | 98% | 47,776 psi | 72% | 2900 fps | 95.7% |
| Vihtavuori 24N41 | <<locked>> | 94% | 53,592 psi | 80% | 2995 fps | 95% |
| Vihtavuori N165 | <<locked>> | 80% | 47,935 psi | 72% | 2760 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 49,487 psi | 74% | 2848 fps | 100% |
| Vihtavuori N170 | <<locked>> | 86% | 44,802 psi | 67% | 2726 fps | 95% |
| Vihtavuori N170 | <<locked>> | 80% | 42,612 psi | 64% | 2746 fps | 95.1% |
| Vihtavuori N555 | <<locked>> | 80% | 56,028 psi | 84% | 2901 fps | 100% |
| Vihtavuori N555 | <<locked>> | 80% | 56,115 psi | 84% | 2963 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 52,721 psi | 79% | 2942 fps | 99.7% |
| Vihtavuori N560 | <<locked>> | 80% | 55,390 psi | 83% | 3054 fps | 100% |
| Vihtavuori N565 | <<locked>> | 80% | 46,572 psi | 70% | 2805 fps | 99.1% |
| Vihtavuori N565 | <<locked>> | 80% | 46,659 psi | 70% | 2874 fps | 99.5% |
| Vihtavuori N568 | <<locked>> | 80% | 41,597 psi | 62% | 2737 fps | 96.9% |
| Vihtavuori N568 | <<locked>> | 80% | 41,829 psi | 63% | 2815 fps | 97.8% |
| Vihtavuori N570 | 85.9 gr | 82% | 43,134 psi | 65% | 2797 fps | 95.4% |
| Vihtavuori N570 | 83.8 gr | 80% | 39,914 psi | 60% | 2805 fps | 95.2% |
| Winchester StaBALL HD | <<locked>> | 80% | 51,837 psi | 78% | 2902 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 80% | 52,141 psi | 78% | 2972 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 52,185 psi | 78% | 2907 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 103 powders for 7.21 Firebird loaded with the .284 | 165gr | Sierra Tipped GameKing. Hodgdon Retumbo delivers the highest muzzle velocity at 3,179 fps; across all powders the maximum-charge window runs from 1,930 fps to 3,179 fps. Accurate 8700 gives the best case fill at 100 %, and 103 of the 103 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 165.0 gr projectile in 0.284" calls for a 1:9.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Accurate 8700, Hodgdon TrailBoss 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. Vihtavuori N570, ADI AR 2218, Hodgdon H1000 rank at the top here: for 7.21 Firebird with the .284 | 165gr | Sierra Tipped GameKing 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.