Load Specifications
Load data in caliber .38 Special with .357 | 125gr | Speer TMJ bullet and 7 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Hodgdon TrailBoss 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 ≥ 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 |
|---|---|---|---|---|---|---|
| Alliant Herco² | <<locked>> | 64% | 17,912 psi | 82% | 1024 fps | 96.7% |
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 68% | 19,232 psi | 88% | 1007 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 17,405 psi | 80% | 932 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 15,940 psi | 73% | 928 fps | 100% |
| SNPE Vectan BA7 1/2*² | <<locked>> | 64% | 19,580 psi | 90% | 1063 fps | 90.7% |
| Vihtavuori N32C Tin Star² | <<locked>> | 72% | 17,840 psi | 82% | 925 fps | 100% |
| Vihtavuori N350*² | <<locked>> | 64% | 19,653 psi | 90% | 1079 fps | 92.2% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 4"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Alliant Herco² | <<locked>> | 60% | 15,853 psi | 73% | 971 fps | 95% |
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 60% | 15,577 psi | 72% | 928 fps | 100% |
| Hodgdon TrailBoss² | 3.7 gr | 60% | 8,122 psi | 37% | 689 fps | 99.6% |
| ReloadSwiss RS 14² | 3.7 gr | 60% | 7,469 psi | 34% | 673 fps | 96.1% |
| SNPE Vectan BA7 1/2*² | <<locked>> | 60% | 17,477 psi | 80% | 1014 fps | 88.7% |
| Vihtavuori N32C Tin Star² | <<locked>> | 60% | 13,663 psi | 63% | 840 fps | 100% |
| Vihtavuori N350*² | <<locked>> | 60% | 17,347 psi | 80% | 1027 fps | 89.9% |
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 | 125gr | Speer TMJ. Vihtavuori N350 delivers the highest muzzle velocity at 1,079 fps; across all powders the maximum-charge window runs from 925 fps to 1,079 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 73–90 %, leaving at least 10 % 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. Hodgdon TrailBoss, ReloadSwiss RS 14 rank at the top here: for .38 Special with the .357 | 125gr | Speer TMJ they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, SNPE Vectan BA7 1/2, Vihtavuori N350 burn incompletely and react more sensitively to barrel length and temperature. Alliant Herco, Baschieri & Pellagri 102 Pistol, Hodgdon TrailBoss 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.