Estimate chamber pressure and muzzle velocity for the 25-20 Winchester with the free, in-browser MyLoads internal-ballistics simulator. The figures below are illustrative estimates from a physics model — not a recommended recipe. Always cross-check a current published loading manual.
| Maximum average pressure (MAP) | 28,000 CUP |
|---|---|
| Nominal case capacity | 13.5 gr H₂O |
| Groove / bullet diameter | 0.257 in (6.53 mm) |
Muzzle velocity
Peak chamber pressure (interval, ±10% burn-rate)
maximum average pressure for this cartridge is specified as 28,000 CUP (CUP is not directly comparable to this psi estimate)
Illustrative example — every figure here is an estimate and can be wrong. Always consult a current published loading manual, and never trust these numbers on their own.
Open the 25-20 Winchester in the MyLoads calculator →