P-Max black powder internal ballistics simulator
Swiss No. 5,   Fg
Swiss No. 4,   1½ Fg
Swiss No. 3,   FFg
Swiss No. 2,   FFFg
Swiss No. 1,   FFFFg
Always check the relevant powder company manual or gun maker manual for maximum loads.
Powder weight:
 grams  grains
Bullet weight:
 grams  grains
Bullet diameter:
 millimetres  inches
Barrel length:
 millimetres  inches
Powder space:
 cc  grains of water
Case length:
 millimetres  inches
Pressure output:
 bar  psi (piezo).  
Velocity output:
 metres/sec.  feet/sec.  
Energy output:
 Joules.  ft-lbs.  

This program is a sister program to the P-Max internal ballistics simulator for modern 'smokeless' nitro powders.

This is a free, online, internal ballistics simulation program for black powder guns. This program is unique, there is no other black powder internal ballistics simulation program available. The purpose of this program is to help you choose which grade of black powder to use and give some idea about its performance. It should be fast enough to be all burnt in the barrel, but the charge should not be so high that the design pressure of the gun is exceeded. This program is still in development, so feedback would be welcome on how you find it performs.

On the one hand, black powder is quite forgiving for overloads of powder compared to nitro powders, as the burning rate is much less dependent on pressure than nitro powders. But on the other hand black powder guns are usually made of soft steels and not designed to contain the same high pressures as guns designed for nitro powders, so some care must be taken in choosing how much of which type of powder to use.

The program is a full numerical simulation with no prior assumptions. It just runs the physics as the virtual charge of powder burns. The burning rate equation for black powder was optimised using the empirical equations by Don Miller (Precision Shooting Annual 1996) and Henning Umland which were in turn based on numerous measurements of muzzle velocity and muzzle energy for practical loads. This program does not use these empirical equations to calculate the muzzle velocity, however.

This program is primarily for small-arms black powder guns, both muzzle loading and cartridge guns. It can be used for cannons, but entering projectile weight and powder charge in grams or grains will be cumbersome! The program was, for example, tested using the load data for the 'Mons Meg' bombard, which shot stone balls of 18 inches diameter, and the results were in reasonable agreement with the recorded performance.

For muzzle-loaders, it is assumed the bullet/ball and wad rammed home on top of the powder charge. The program calculates the powder space taken up by the powder charge, which takes up all the space behind the bullet. It is assumed that there is no pressure loss due to the primer hole in muzzle loading guns. For cartridge guns, the powder space for the cartridge must be entered. The 'Powder Space' is the space in an empty case (no powder) behind a bullet which has been seated into the case. See this short video on how you can easily measure powder space. The program assumes that the bullet is seated into the case to a depth of one calibre.