Load Specifications
Load data in caliber 8 x 58 R with .318 | 122gr | Sax MJG-SX bullet and 4 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 14 and Hodgdon TrailBoss.
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: 23.62"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AR 2207 | <<locked>> | 84% | 27,760 psi | 87% | 2375 fps | 96% |
| Hodgdon TrailBoss | <<locked>> | 98% | 28,137 psi | 88% | 1627 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 28,239 psi | 89% | 1677 fps | 100% |
| Vihtavuori N120 | <<locked>> | 84% | 28,181 psi | 88% | 2356 fps | 97.4% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 23.62"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AR 2207 | <<locked>> | 82% | 26,237 psi | 82% | 2329 fps | 95.3% |
| Hodgdon TrailBoss | 9 gr | 80% | 20,943 psi | 66% | 1463 fps | 100% |
| ReloadSwiss RS 14 | 9.2 gr | 80% | 20,610 psi | 65% | 1496 fps | 100% |
| Vihtavuori N120 | <<locked>> | 80% | 25,135 psi | 79% | 2267 fps | 96.1% |
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 4 powders for 8 x 58 R loaded with the .318 | 122gr | Sax MJG-SX. ADI AR 2207 delivers the highest muzzle velocity at 2,375 fps; across all powders the maximum-charge window runs from 1,627 fps to 2,375 fps. ReloadSwiss RS 14 gives the best case fill at 100 %, and 4 of the 4 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (220 MPa), the top charges use 87–89 %, leaving at least 11 % headroom. The 122.0 gr projectile in 0.318" calls for a 1:11.0 twist; slower twists will usually not stabilise this weight. 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. ReloadSwiss RS 14, Hodgdon TrailBoss rank at the top here: for 8 x 58 R with the .318 | 122gr | Sax MJG-SX 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.