Load Specifications
Load data in caliber .38 Long Colt with .355 | 124gr | Geco FMJ bullet and 4 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are 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 |
|---|---|---|---|---|---|---|
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 68% | 10,965 psi | 84% | 758 fps | 97.8% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 10,573 psi | 81% | 715 fps | 99.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 9,166 psi | 70% | 689 fps | 95% |
| Vihtavuori N32C Tin Star² | <<locked>> | 76% | 11,806 psi | 90% | 748 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 |
|---|---|---|---|---|---|---|
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 60% | 8,833 psi | 68% | 692 fps | 95.1% |
| Hodgdon TrailBoss*² | 1.8 gr | 60% | 5,091 psi | 39% | 512 fps | 90.1% |
| ReloadSwiss RS 14*² | <<locked>> | 68% | 5,598 psi | 43% | 545 fps | 86.3% |
| Vihtavuori N32C Tin Star² | <<locked>> | 60% | 7,702 psi | 59% | 633 fps | 99.6% |
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 4 powders for .38 Long Colt loaded with the .355 | 124gr | Geco FMJ. Baschieri & Pellagri 102 Pistol delivers the highest muzzle velocity at 758 fps; across all powders the maximum-charge window runs from 689 fps to 758 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 2 of the 4 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (90 MPa), the top charges use 70–90 %, 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 rank at the top here: for .38 Long Colt with the .355 | 124gr | Geco FMJ they combine a high case fill with complete burn and sit in the upper velocity band. Baschieri & Pellagri 102 Pistol, Hodgdon TrailBoss, ReloadSwiss RS 14 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.