Estimate chamber pressure and muzzle velocity for the 38-40 Winchester with the free, in-browser MyLoads internal ballistics simulator. The figures below are illustrative estimates from a physics model — not a recommended load. Always cross-check a current published loading manual.
| Maximum average pressure (MAP) | 14,000 CUP |
|---|---|
| Nominal case capacity | 39.5 gr H₂O |
| Groove / bullet diameter | 0.400 in (10.16 mm) |
Muzzle velocity
Peak chamber pressure (interval, ±10% burn rate)
MAP for this cartridge is specified as 14,000 CUP (CUP is not directly comparable to this psi estimate)
The simulator isn't optimized for this cartridge yet and may read pressure high and velocity high.
Illustrative example — every figure is an estimate; always confirm your load against a current published manual before loading.
Powders and bullets handloaders commonly use for the 38-40 Winchester, drawn from public discussion and listed most common first. They appear as the Popular group in the calculator's pickers. This is not a load recommendation — always check your load against a current published manual.
Use MyLoads as a 38-40 Winchester velocity and pressure calculator: it estimates muzzle velocity, muzzle energy and the full chamber-pressure curve for your own powder, charge and barrel length, compared against the reference facts above.
Open the 38-40 Winchester in the MyLoads calculator →