Load Specifications
Load data in caliber .38 Special with .357 | 170gr | Speer SP MAG GD bullet and 7 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 ≥ 60% and propellant combustion ≥ 80%. 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: 4"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AP 100*² | <<locked>> | 68% | 18,550 psi | 85% | 883 fps | 88.4% |
| Alliant Herco² | <<locked>> | 64% | 18,681 psi | 86% | 866 fps | 99.5% |
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 64% | 18,057 psi | 83% | 807 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 17,840 psi | 82% | 768 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 16,491 psi | 76% | 771 fps | 100% |
| Rottweil P 806*² | <<locked>> | 64% | 18,565 psi | 85% | 932 fps | 92.8% |
| Vihtavuori N32C Tin Star² | <<locked>> | 72% | 18,652 psi | 86% | 764 fps | 100% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 4"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| ADI AP 100*² | <<locked>> | 64% | 16,505 psi | 76% | 840 fps | 86.1% |
| Alliant Herco² | <<locked>> | 60% | 16,505 psi | 76% | 823 fps | 98.6% |
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 60% | 16,331 psi | 75% | 778 fps | 100% |
| Hodgdon TrailBoss² | 2.9 gr | 60% | 8,311 psi | 38% | 571 fps | 100% |
| ReloadSwiss RS 14² | 3 gr | 60% | 7,992 psi | 37% | 571 fps | 99.3% |
| Rottweil P 806*² | <<locked>> | 60% | 15,969 psi | 73% | 879 fps | 90% |
| Vihtavuori N32C Tin Star² | <<locked>> | 60% | 13,837 psi | 64% | 686 fps | 100% |
Recommended = one of the top powders for this cartridge and bullet combination.
* 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.
This overview compares 7 powders for .38 Special loaded with the .357 | 170gr | Speer SP MAG GD. Rottweil P 806 delivers the highest muzzle velocity at 932 fps; across all powders the maximum-charge window runs from 764 fps to 932 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 2 of the 7 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (150 MPa), the top charges use 76–86 %, leaving at least 14 % headroom. 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. ReloadSwiss RS 14, Hodgdon TrailBoss rank at the top here: for .38 Special with the .357 | 170gr | Speer SP MAG GD they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, ADI AP 100, Rottweil P 806 burn incompletely and react more sensitively to barrel length and temperature. ADI AP 100, Alliant Herco, Baschieri & Pellagri 102 Pistol stay subsonic at start load. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.