What this program does
Given the various inputs listed above, the program simulates the evolution of the gas pressure and the velocity of the bullet as it travels up the barrel. This program is a numerical simulation. It makes no prior assumptions about pressure rise or any other variable. It just runs the basic physics of what happens next as the virtual charge of powder burns. A summary of the results are given. Graphs are plotted for pressure -vs- time, pressure -vs- distance along the barrel, and bullet velocity -vs- distance along the barrel.Here is a short youtube movie about the P-Max internal ballistics simulator.
Using the program
This simulator is not intended to replace the relevant reloading manual as a guide to good starting loads or safe maximum loads. You should follow safe reloading practices at all times.
While this simulator is designed to be intuitive and easy to use, it is strongly suggested that you read the manual for this simulator. It will help you get sensible and realistic results.*Powder space is the capacity in the case behind the loaded bullet, with no powder in the case. This was called "usable case capacity", but there was too much confusion between this and the case capacity to the case mouth, so it was changed to something less ambiguous. See a list of powder spaces for most of the popular rifle and pistol cartridges to get you started, and see this short video on how you can easily measure powder space.
For black powder guns, see our new black powder internal ballistics simulator.