Load data for 7.21 Firebird (Lazzeroni) + .284 | 175gr | Sierra SBT GameKing
Recommended Powder(s):
Load Specifications
(Use the Personalized Load Calculator below to adjust )
Bullet: | .284 | 175gr | Sierra SBT GameKing |
Manufacturer SKU: | 1940 |
Bullet Weight: | 175gr | 11.3g |
Bullet Diameter: | 0.284" | 7.21mm |
Bullet Length: | <<locked>> |
Caliber: | 7.21 Firebird (Lazzeroni) load data |
Case Length (l3): | 2.800" | 71.1mm |
Cartridge Length (C.O.L.): | <<locked>> |
Seated Depth: | <<locked>> |
Shank Seated Depth: | <<locked>> |
Case Capacity: | 121.0 Grains of Water | 7.86 cm³ |
Primer Size: | Large Rifle Magnum (LRM) |
Max. allowed Pressure: | 66717 psi | 4600 bar |
LID: | LID_B5854_C1103 |
Last updated: | 2026-02-22 |
Recommended Twist Rate: | 1:10 - 1:9 |
Load data for 70 loads in caliber 7.21 Firebird (Lazzeroni) with .284 | 175gr | Sierra SBT GameKing bullet and 35 powder(s). The key underlying parameters are shown in the table above.
Important Notice: DO NOT go below Minimum Charge or above Maximum Charge unless there are reasons. Since xxlreloading.com has no control over the equipment and components used by the customer and the data used in connection with the website, any responsibility and liability for the results achieved is rejected. Also see our Terms of Service.
Questions regarding the load data: Please read the information in the next tab "Explanations".
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A load must fulfill certain criteria to be listed in the default view below - see "powder criteria to fulfill to be listed".
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Our load data might deviate from other sources - see the "most common reasons for deviations".
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All loads are based on the bullet and case dimensions shown under "Load Specifications" - see "reloading suggestions" if you deviate.
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You can set your specifications in the "Personalized Load Calculator".
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Use the Personalized Load Calculator to customize loads to your own specific requirements. Find more details in the help section.
Our default view only displays powders/loads that fulfill certain criteria: Max pressure of a load <=90% of Max. Standardized Pressure. Fill Rate (Min FR): >80% and <100% for rife loads, >60% and <100% for pistol loads. Min. Propellant Combustion (Min z): >90% for rifle loads , >80% for pistol/revolver loads. Relax these criteria at your own risk to potentially get more powders shown in the load tables.
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Click on the desired row in the tables below to add a specific load / powder to your Diary and manage there.
Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
ADI AR 2217 | 90% | 89% | 100% | |||
ADI AR 2218 | 93% | 89% | 100% | |||
ADI AR 2225 | 92% | 90% | 100% | |||
Accurate 8700 | 97% | 82% | 99% | |||
Alliant Reloder-25 | 86% | 89% | 100% | |||
Alliant Reloder-33 | 90% | 90% | 100% | |||
Alliant Reloder-50 | 94% | 90% | 99% | |||
Baschieri & Pellagri 109 | 84% | 89% | 100% | |||
Bofors RP15 | 84% | 89% | 100% | |||
Bofors RP30 | 88% | 89% | 100% | |||
Hodgdon 50BMG | 97% | 87% | 93% | |||
Hodgdon H1000 | 90% | 89% | 100% | |||
Hodgdon H4831 | 85% | 90% | 100% | |||
Hodgdon Retumbo | 92% | 90% | 100% | |||
Hodgdon US 869 | 97% | 89% | 96% | |||
Hodgdon TrailBoss | 96% | 55% | 100% | |||
IMR 4955 Enduron | 83% | 90% | 100% | |||
IMR 7977 Enduron | 88% | 89% | 98% | |||
IMR 8133 Enduron | 94% | 89% | 100% | |||
Lovex D100 | 91% | 90% | 97% | |||
Lovex S071 | 87% | 89% | 100% | |||
Norma 217 | 93% | 89% | 100% | |||
Ramshot LRT | 94% | 90% | 97% | |||
ReloadSwiss RS 14 | 97% | 57% | 100% | |||
ReloadSwiss RS 76 | 85% | 90% | 100% | |||
ReloadSwiss RS 80 | 88% | 90% | 100% | |||
SNPE Vectan SP 13 | 97% | 84% | 99% | |||
Shooters World 50 BMG | 91% | 90% | 97% | |||
Vihtavuori 20N29 | 97% | 83% | 97% | |||
Vihtavuori 24N41 | 94% | 89% | 96% | |||
Vihtavuori N165 | 85% | 89% | 100% | |||
Vihtavuori N170 | 93% | 90% | 99% | |||
Vihtavuori N565 | 85% | 89% | 100% | |||
Vihtavuori N568 | 88% | 90% | 100% | |||
Vihtavuori N570 | 89% | 90% | 99% |
Max Load - Barrel Length: 23.60''
Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
ADI AR 2217 | <<locked>> | 81% | 43511 | 65% | **84 | 99% |
[ADI AR 2218]* | <<locked>> | 81% | 37565 | 56% | **18 | 94% |
ADI AR 2225 | <<locked>> | 81% | 40930 | 61% | **54 | 100% |
[Accurate 8700]* | <<locked>> | 82% | 31241 | 47% | **82 | 90% |
Alliant Reloder-25 | <<locked>> | 81% | 50473 | 76% | **92 | 100% |
Alliant Reloder-33 | <<locked>> | 81% | 42119 | 63% | **87 | 96% |
[Alliant Reloder-50]* | <<locked>> | 81% | 36898 | 55% | **49 | 93% |
Baschieri & Pellagri 109 | <<locked>> | 81% | 53272 | 80% | **22 | 99% |
Bofors RP15 | <<locked>> | 81% | 53882 | 81% | **48 | 100% |
Bofors RP30 | <<locked>> | 81% | 47152 | 71% | **49 | 100% |
[Hodgdon 50BMG]* | <<locked>> | 92% | 49458 | 74% | **95 | 90% |
Hodgdon H1000 | <<locked>> | 81% | 43511 | 65% | **84 | 99% |
Hodgdon H4831 | <<locked>> | 81% | 52344 | 78% | **02 | 100% |
Hodgdon Retumbo | <<locked>> | 81% | 40930 | 61% | **54 | 100% |
[Hodgdon US 869]* | <<locked>> | 86% | 40959 | 61% | **08 | 90% |
Hodgdon TrailBoss | <<locked>> | 81% | 29428 | 44% | **99 | 100% |
IMR 4955 Enduron | <<locked>> | 81% | 55448 | 83% | **31 | 100% |
IMR 7977 Enduron | <<locked>> | 81% | 47485 | 71% | **71 | 95% |
IMR 8133 Enduron | <<locked>> | 81% | 37971 | 57% | **69 | 98% |
[Lovex D100]* | <<locked>> | 81% | 41887 | 63% | **89 | 92% |
Lovex S071 | <<locked>> | 81% | 49574 | 74% | **00 | 100% |
Norma 217 | <<locked>> | 81% | 39102 | 59% | **12 | 100% |
[Ramshot LRT]* | <<locked>> | 83% | 40901 | 61% | **54 | 90% |
ReloadSwiss RS 14 | <<locked>> | 81% | 30255 | 45% | **39 | 100% |
ReloadSwiss RS 76 | <<locked>> | 81% | 50575 | 76% | **58 | 100% |
ReloadSwiss RS 80 | <<locked>> | 81% | 46224 | 69% | **62 | 99% |
[SNPE Vectan SP 13]* | <<locked>> | 81% | 32605 | 49% | **02 | 91% |
[Shooters World 50 BMG]* | <<locked>> | 81% | 41887 | 63% | **89 | 92% |
[Vihtavuori 20N29]* | <<locked>> | 85% | 35766 | 54% | **87 | 90% |
[Vihtavuori 24N41]* | <<locked>> | 83% | 40814 | 61% | **12 | 90% |
Vihtavuori N165 | <<locked>> | 81% | 52837 | 79% | **72 | 100% |
[Vihtavuori N170]* | <<locked>> | 81% | 40857 | 61% | **72 | 94% |
Vihtavuori N565 | <<locked>> | 81% | 51750 | 78% | **22 | 100% |
Vihtavuori N568 | <<locked>> | 81% | 46847 | 70% | **62 | 99% |
Vihtavuori N570 | <<locked>> | 81% | 45324 | 68% | **69 | 97% |
Start Load - Barrel Length: 23.60''
Any powder missing? Then click here.
FR ... fill rate of the cartridge in percent
MaxP ... max. pressure of load in psi or bar
% ... max. pressure of load in percent of the maximum allowed pressure for this caliber
V(0) ... muzzle velocity in feet per second (fps) or meters per second (m/s)
z ... powder burnt in percent
[...] *... not dangerous but load has suboptimal powder burnt with possible characteristics such as extensive muzzle flash or inaccurate loads.
[...] ²... fill rate low - you might want to consider using a filler to ensure proper ignition.
[...] ᴾ... possible press load - work up slowly to this load while watching for signs of excessive pressure.
👍 ... recommended powder/load for this caliber and bullet combination based on its ballistic performance.
<<locked>>... you need to buy an access license to unlock the data