Load Specifications
Load data in caliber 9 x 57 Mauser with .358 | 125gr | Rim Rock RNFP Cowboy bullet and 8 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2207, Vihtavuori N120 and ReloadSwiss RS 14.
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>> | 90% | 35,897 psi | 88% | 2995 fps | 98.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 28,747 psi | 71% | 1978 fps | 100% |
| IMR 4227 | <<locked>> | 82% | 35,694 psi | 88% | 2887 fps | 97.3% |
| Lovex S053 | <<locked>> | 84% | 36,680 psi | 90% | 2917 fps | 99.7% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 27,876 psi | 69% | 2018 fps | 100% |
| ReloadSwiss RS 36 | <<locked>> | 84% | 36,738 psi | 90% | 2956 fps | 97.5% |
| SNPE Vectan BA6 1/2 | <<locked>> | 86% | 36,230 psi | 89% | 2779 fps | 100% |
| Vihtavuori N120 | <<locked>> | 90% | 36,230 psi | 89% | 2966 fps | 99.4% |
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 | 42.9 gr | 82% | 27,412 psi | 68% | 2759 fps | 95.8% |
| Hodgdon TrailBoss | <<locked>> | 80% | 20,639 psi | 51% | 1765 fps | 100% |
| IMR 4227 | <<locked>> | 80% | 33,518 psi | 83% | 2828 fps | 96.6% |
| Lovex S053 | <<locked>> | 80% | 32,213 psi | 79% | 2805 fps | 99% |
| ReloadSwiss RS 14 | 15.4 gr | 80% | 20,102 psi | 50% | 1804 fps | 100% |
| ReloadSwiss RS 36 | <<locked>> | 80% | 32,097 psi | 79% | 2835 fps | 96% |
| SNPE Vectan BA6 1/2 | <<locked>> | 80% | 30,371 psi | 75% | 2648 fps | 100% |
| Vihtavuori N120 | 41.8 gr | 80% | 25,962 psi | 64% | 2680 fps | 96.4% |
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 19 powders for 9 x 57 Mauser loaded with the .358 | 125gr | Rim Rock RNFP Cowboy. ADI AR 2207 delivers the highest muzzle velocity at 2,995 fps; across all powders the maximum-charge window runs from 1,978 fps to 2,995 fps. Accurate 2015 gives the best case fill at 100 %, and 19 of the 19 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (280 MPa), the top charges use 69–90 %, leaving at least 10 % headroom. Accurate 2015, Alliant AR-Comp, 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. ADI AR 2207, Vihtavuori N120, ReloadSwiss RS 14 rank at the top here: for 9 x 57 Mauser with the .358 | 125gr | Rim Rock RNFP Cowboy they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Accurate 1680, Accurate 2015, Alliant AR-Comp 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.