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Internal Ballistics

The BBT "P-Max" internal ballistics simulator

Powder type
Chemie Swiss
Powder space*:
 cc  grains of water
Powder weight:
 grams  grains
Bullet weight:
 grams  grains
Bullet type:
 Copper jacketed, lead core ( moly'd)
 Bore rider with thin drive bands
 Monolithic solid
Barrel length:
 millimetres  inches
Case length:
 millimetres  inches
Pressure output:
 bar  psi (piezo).  
Velocity output:
 metres/sec.  feet/sec.  
Muzzle energy output:
 Joules.  ft-lbs.  

This program does not take the place of a reloading manual published by the relevant powder company for estimating starting loads or maximum loads.

What this program does
This is a free, online, internal ballistics simulation program. There is no other online program like it. There are no issues with operating systems - so long as your device has a browser and can access the Internet, you can use this simulator. There are no problems with getting the latest update. As soon as the simulator or its data libraries are updated, those updates are available next time you use this simulator.

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
The purpose of this simulator is to help you select the right powder for your particular cartridge/calibre/bullet combination and to give you a reasonable idea of the performance you might expect. However, the place to do load development is on a range with your particular firearm, not on a keyboard in front of a computer.

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.

Version 2.8