Load Specifications
Load data in caliber .38 Long Colt with .355 | 124gr | X-TREME FMJ bullet and 3 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 |
|---|---|---|---|---|---|---|
| Hodgdon TrailBoss | <<locked>> | 92% | 11,342 psi | 87% | 709 fps | 99.8% |
| ReloadSwiss RS 14 | <<locked>> | 96% | 11,298 psi | 87% | 722 fps | 97.7% |
| Vihtavuori N32C Tin Star² | <<locked>> | 64% | 10,776 psi | 83% | 692 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 |
|---|---|---|---|---|---|---|
| Hodgdon TrailBoss² | 1.8 gr | 60% | 6,875 psi | 53% | 548 fps | 95.6% |
| ReloadSwiss RS 14*² | 1.9 gr | 60% | 6,889 psi | 53% | 554 fps | 91% |
| Vihtavuori N32C Tin Star² | <<locked>> | 60% | 10,211 psi | 78% | 676 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.
This overview compares 3 powders for .38 Long Colt loaded with the .355 | 124gr | X-TREME FMJ. ReloadSwiss RS 14 delivers the highest muzzle velocity at 722 fps; across all powders the maximum-charge window runs from 692 fps to 722 fps. ReloadSwiss RS 14 gives the best case fill at 96 %, and 2 of the 3 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (90 MPa), the top charges use 83–87 %, leaving at least 13 % headroom. Hodgdon TrailBoss, ReloadSwiss RS 14 rank at the top here: for .38 Long Colt with the .355 | 124gr | X-TREME FMJ they combine a high case fill with complete burn and sit in the upper velocity band. Hodgdon TrailBoss, ReloadSwiss RS 14, Vihtavuori N32C Tin Star 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.