Estimate chamber pressure and muzzle velocity for the 303 British 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) | 49,000 psi |
|---|---|
| Nominal case capacity | 56.5 gr H₂O |
| Groove / bullet diameter | 0.314 in (7.98 mm) |
Muzzle velocity
Peak chamber pressure (interval, ±10% burn rate)
nominal is 69% MAP (49,000 psi)
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 303 British, 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 303 British 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 303 British in the MyLoads calculator →