There is a great amount of information available about velocities, trajectories, and general ballistics of firearm projectiles, but most of it describes what happens from the time the bullet leaves the muzzle.

Does anyone know of a source of information describing the pressures, velocities, acceleration, etc from primer ignition to muzzle? I realize that all of these average values can be easily calculated, but I'm interested in how they change as the projectile moves through the barrel. I don't imagine that it's linear.

(I was required to attend a meeting yesterday that neither benefited from my attendance, nor provided me with much useful info, so my mind wandered to such musings.)